use core::{
borrow::Borrow,
panic::{RefUnwindSafe, UnwindSafe},
};
use alloc::{boxed::Box, sync::Arc, vec, vec::Vec};
use regex_syntax::{
ast,
hir::{self, Hir},
};
use crate::{
meta::{
error::BuildError,
strategy::{self, Strategy},
wrappers,
},
nfa::thompson::WhichCaptures,
util::{
captures::{Captures, GroupInfo},
iter,
pool::{Pool, PoolGuard},
prefilter::Prefilter,
primitives::{NonMaxUsize, PatternID},
search::{HalfMatch, Input, Match, MatchKind, PatternSet, Span},
},
};
/// A type alias for our pool of meta::Cache that fixes the type parameters to
/// what we use for the meta regex below.
type CachePool = Pool<Cache, CachePoolFn>;
/// Same as above, but for the guard returned by a pool.
type CachePoolGuard<'a> = PoolGuard<'a, Cache, CachePoolFn>;
/// The type of the closure we use to create new caches. We need to spell out
/// all of the marker traits or else we risk leaking !MARKER impls.
type CachePoolFn =
Box<dyn Fn() -> Cache + Send + Sync + UnwindSafe + RefUnwindSafe>;
/// A regex matcher that works by composing several other regex matchers
/// automatically.
///
/// In effect, a meta regex papers over a lot of the quirks or performance
/// problems in each of the regex engines in this crate. Its goal is to provide
/// an infallible and simple API that "just does the right thing" in the common
/// case.
///
/// A meta regex is the implementation of a `Regex` in the `regex` crate.
/// Indeed, the `regex` crate API is essentially just a light wrapper over
/// this type. This includes the `regex` crate's `RegexSet` API!
///
/// # Composition
///
/// This is called a "meta" matcher precisely because it uses other regex
/// matchers to provide a convenient high level regex API. Here are some
/// examples of how other regex matchers are composed:
///
/// * When calling [`Regex::captures`], instead of immediately
/// running a slower but more capable regex engine like the
/// [`PikeVM`](crate::nfa::thompson::pikevm::PikeVM), the meta regex engine
/// will usually first look for the bounds of a match with a higher throughput
/// regex engine like a [lazy DFA](crate::hybrid). Only when a match is found
/// is a slower engine like `PikeVM` used to find the matching span for each
/// capture group.
/// * While higher throughout engines like the lazy DFA cannot handle
/// Unicode word boundaries in general, they can still be used on pure ASCII
/// haystacks by pretending that Unicode word boundaries are just plain ASCII
/// word boundaries. However, if a haystack is not ASCII, the meta regex engine
/// will automatically switch to a (possibly slower) regex engine that supports
/// Unicode word boundaries in general.
/// * In some cases where a regex pattern is just a simple literal or a small
/// set of literals, an actual regex engine won't be used at all. Instead,
/// substring or multi-substring search algorithms will be employed.
///
/// There are many other forms of composition happening too, but the above
/// should give a general idea. In particular, it may perhaps be surprising
/// that *multiple* regex engines might get executed for a single search. That
/// is, the decision of what regex engine to use is not _just_ based on the
/// pattern, but also based on the dynamic execution of the search itself.
///
/// The primary reason for this composition is performance. The fundamental
/// tension is that the faster engines tend to be less capable, and the more
/// capable engines tend to be slower.
///
/// Note that the forms of composition that are allowed are determined by
/// compile time crate features and configuration. For example, if the `hybrid`
/// feature isn't enabled, or if [`Config::hybrid`] has been disabled, then the
/// meta regex engine will never use a lazy DFA.
///
/// # Synchronization and cloning
///
/// Most of the regex engines in this crate require some kind of mutable
/// "scratch" space to read and write from while performing a search. Since
/// a meta regex composes these regex engines, a meta regex also requires
/// mutable scratch space. This scratch space is called a [`Cache`].
///
/// Most regex engines _also_ usually have a read-only component, typically
/// a [Thompson `NFA`](crate::nfa::thompson::NFA).
///
/// In order to make the `Regex` API convenient, most of the routines hide
/// the fact that a `Cache` is needed at all. To achieve this, a [memory
/// pool](crate::util::pool::Pool) is used internally to retrieve `Cache`
/// values in a thread safe way that also permits reuse. This in turn implies
/// that every such search call requires some form of synchronization. Usually
/// this synchronization is fast enough to not notice, but in some cases, it
/// can be a bottleneck. This typically occurs when all of the following are
/// true:
///
/// * The same `Regex` is shared across multiple threads simultaneously,
/// usually via a [`util::lazy::Lazy`](crate::util::lazy::Lazy) or something
/// similar from the `once_cell` or `lazy_static` crates.
/// * The primary unit of work in each thread is a regex search.
/// * Searches are run on very short haystacks.
///
/// This particular case can lead to high contention on the pool used by a
/// `Regex` internally, which can in turn increase latency to a noticeable
/// effect. This cost can be mitigated in one of the following ways:
///
/// * Use a distinct copy of a `Regex` in each thread, usually by cloning it.
/// Cloning a `Regex` _does not_ do a deep copy of its read-only component.
/// But it does lead to each `Regex` having its own memory pool, which in
/// turn eliminates the problem of contention. In general, this technique should
/// not result in any additional memory usage when compared to sharing the same
/// `Regex` across multiple threads simultaneously.
/// * Use lower level APIs, like [`Regex::search_with`], which permit passing
/// a `Cache` explicitly. In this case, it is up to you to determine how best
/// to provide a `Cache`. For example, you might put a `Cache` in thread-local
/// storage if your use case allows for it.
///
/// Overall, this is an issue that happens rarely in practice, but it can
/// happen.
///
/// # Warning: spin-locks may be used in alloc-only mode
///
/// When this crate is built without the `std` feature and the high level APIs
/// on a `Regex` are used, then a spin-lock will be used to synchronize access
/// to an internal pool of `Cache` values. This may be undesirable because
/// a spin-lock is [effectively impossible to implement correctly in user
/// space][spinlocks-are-bad]. That is, more concretely, the spin-lock could
/// result in a deadlock.
///
/// [spinlocks-are-bad]: https://matklad.github.io/2020/01/02/spinlocks-considered-harmful.html
///
/// If one wants to avoid the use of spin-locks when the `std` feature is
/// disabled, then you must use APIs that accept a `Cache` value explicitly.
/// For example, [`Regex::search_with`].
///
/// # Example
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r"^[0-9]{4}-[0-9]{2}-[0-9]{2}$")?;
/// assert!(re.is_match("2010-03-14"));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: anchored search
///
/// This example shows how to use [`Input::anchored`] to run an anchored
/// search, even when the regex pattern itself isn't anchored. An anchored
/// search guarantees that if a match is found, then the start offset of the
/// match corresponds to the offset at which the search was started.
///
/// ```
/// use regex_automata::{meta::Regex, Anchored, Input, Match};
///
/// let re = Regex::new(r"\bfoo\b")?;
/// let input = Input::new("xx foo xx").range(3..).anchored(Anchored::Yes);
/// // The offsets are in terms of the original haystack.
/// assert_eq!(Some(Match::must(0, 3..6)), re.find(input));
///
/// // Notice that no match occurs here, because \b still takes the
/// // surrounding context into account, even if it means looking back
/// // before the start of your search.
/// let hay = "xxfoo xx";
/// let input = Input::new(hay).range(2..).anchored(Anchored::Yes);
/// assert_eq!(None, re.find(input));
/// // Indeed, you cannot achieve the above by simply slicing the
/// // haystack itself, since the regex engine can't see the
/// // surrounding context. This is why 'Input' permits setting
/// // the bounds of a search!
/// let input = Input::new(&hay[2..]).anchored(Anchored::Yes);
/// // WRONG!
/// assert_eq!(Some(Match::must(0, 0..3)), re.find(input));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: earliest search
///
/// This example shows how to use [`Input::earliest`] to run a search that
/// might stop before finding the typical leftmost match.
///
/// ```
/// use regex_automata::{meta::Regex, Anchored, Input, Match};
///
/// let re = Regex::new(r"[a-z]{3}|b")?;
/// let input = Input::new("abc").earliest(true);
/// assert_eq!(Some(Match::must(0, 1..2)), re.find(input));
///
/// // Note that "earliest" isn't really a match semantic unto itself.
/// // Instead, it is merely an instruction to whatever regex engine
/// // gets used internally to quit as soon as it can. For example,
/// // this regex uses a different search technique, and winds up
/// // producing a different (but valid) match!
/// let re = Regex::new(r"abc|b")?;
/// let input = Input::new("abc").earliest(true);
/// assert_eq!(Some(Match::must(0, 0..3)), re.find(input));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: change the line terminator
///
/// This example shows how to enable multi-line mode by default and change
/// the line terminator to the NUL byte:
///
/// ```
/// use regex_automata::{meta::Regex, util::syntax, Match};
///
/// let re = Regex::builder()
/// .syntax(syntax::Config::new().multi_line(true))
/// .configure(Regex::config().line_terminator(b'\x00'))
/// .build(r"^foo$")?;
/// let hay = "\x00foo\x00";
/// assert_eq!(Some(Match::must(0, 1..4)), re.find(hay));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[derive(Debug)]
pub struct Regex {
/// The actual regex implementation.
imp: Arc<RegexI>,
/// A thread safe pool of caches.
///
/// For the higher level search APIs, a `Cache` is automatically plucked
/// from this pool before running a search. The lower level `with` methods
/// permit the caller to provide their own cache, thereby bypassing
/// accesses to this pool.
///
/// Note that we put this outside the `Arc` so that cloning a `Regex`
/// results in creating a fresh `CachePool`. This in turn permits callers
/// to clone regexes into separate threads where each such regex gets
/// the pool's "thread owner" optimization. Otherwise, if one shares the
/// `Regex` directly, then the pool will go through a slower mutex path for
/// all threads except for the "owner."
pool: CachePool,
}
/// The internal implementation of `Regex`, split out so that it can be wrapped
/// in an `Arc`.
#[derive(Debug)]
struct RegexI {
/// The core matching engine.
///
/// Why is this reference counted when RegexI is already wrapped in an Arc?
/// Well, we need to capture this in a closure to our `Pool` below in order
/// to create new `Cache` values when needed. So since it needs to be in
/// two places, we make it reference counted.
///
/// We make `RegexI` itself reference counted too so that `Regex` itself
/// stays extremely small and very cheap to clone.
strat: Arc<dyn Strategy>,
/// Metadata about the regexes driving the strategy. The metadata is also
/// usually stored inside the strategy too, but we put it here as well
/// so that we can get quick access to it (without virtual calls) before
/// executing the regex engine. For example, we use this metadata to
/// detect a subset of cases where we know a match is impossible, and can
/// thus avoid calling into the strategy at all.
///
/// Since `RegexInfo` is stored in multiple places, it is also reference
/// counted.
info: RegexInfo,
}
/// Convenience constructors for a `Regex` using the default configuration.
impl Regex {
/// Builds a `Regex` from a single pattern string using the default
/// configuration.
///
/// If there was a problem parsing the pattern or a problem turning it into
/// a regex matcher, then an error is returned.
///
/// If you want to change the configuration of a `Regex`, use a [`Builder`]
/// with a [`Config`].
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Match};
///
/// let re = Regex::new(r"(?Rm)^foo$")?;
/// let hay = "\r\nfoo\r\n";
/// assert_eq!(Some(Match::must(0, 2..5)), re.find(hay));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn new(pattern: &str) -> Result<Regex, BuildError> {
Regex::builder().build(pattern)
}
/// Builds a `Regex` from many pattern strings using the default
/// configuration.
///
/// If there was a problem parsing any of the patterns or a problem turning
/// them into a regex matcher, then an error is returned.
///
/// If you want to change the configuration of a `Regex`, use a [`Builder`]
/// with a [`Config`].
///
/// # Example: simple lexer
///
/// This simplistic example leverages the multi-pattern support to build a
/// simple little lexer. The pattern ID in the match tells you which regex
/// matched, which in turn might be used to map back to the "type" of the
/// token returned by the lexer.
///
/// ```
/// use regex_automata::{meta::Regex, Match};
///
/// let re = Regex::new_many(&[
/// r"[[:space:]]",
/// r"[A-Za-z0-9][A-Za-z0-9_]+",
/// r"->",
/// r".",
/// ])?;
/// let haystack = "fn is_boss(bruce: i32, springsteen: String) -> bool;";
/// let matches: Vec<Match> = re.find_iter(haystack).collect();
/// assert_eq!(matches, vec![
/// Match::must(1, 0..2), // 'fn'
/// Match::must(0, 2..3), // ' '
/// Match::must(1, 3..10), // 'is_boss'
/// Match::must(3, 10..11), // '('
/// Match::must(1, 11..16), // 'bruce'
/// Match::must(3, 16..17), // ':'
/// Match::must(0, 17..18), // ' '
/// Match::must(1, 18..21), // 'i32'
/// Match::must(3, 21..22), // ','
/// Match::must(0, 22..23), // ' '
/// Match::must(1, 23..34), // 'springsteen'
/// Match::must(3, 34..35), // ':'
/// Match::must(0, 35..36), // ' '
/// Match::must(1, 36..42), // 'String'
/// Match::must(3, 42..43), // ')'
/// Match::must(0, 43..44), // ' '
/// Match::must(2, 44..46), // '->'
/// Match::must(0, 46..47), // ' '
/// Match::must(1, 47..51), // 'bool'
/// Match::must(3, 51..52), // ';'
/// ]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// One can write a lexer like the above using a regex like
/// `(?P<space>[[:space:]])|(?P<ident>[A-Za-z0-9][A-Za-z0-9_]+)|...`,
/// but then you need to ask whether capture group matched to determine
/// which branch in the regex matched, and thus, which token the match
/// corresponds to. In contrast, the above example includes the pattern ID
/// in the match. There's no need to use capture groups at all.
///
/// # Example: finding the pattern that caused an error
///
/// When a syntax error occurs, it is possible to ask which pattern
/// caused the syntax error.
///
/// ```
/// use regex_automata::{meta::Regex, PatternID};
///
/// let err = Regex::new_many(&["a", "b", r"\p{Foo}", "c"]).unwrap_err();
/// assert_eq!(Some(PatternID::must(2)), err.pattern());
/// ```
///
/// # Example: zero patterns is valid
///
/// Building a regex with zero patterns results in a regex that never
/// matches anything. Because this routine is generic, passing an empty
/// slice usually requires a turbo-fish (or something else to help type
/// inference).
///
/// ```
/// use regex_automata::{meta::Regex, util::syntax, Match};
///
/// let re = Regex::new_many::<&str>(&[])?;
/// assert_eq!(None, re.find(""));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn new_many<P: AsRef<str>>(
patterns: &[P],
) -> Result<Regex, BuildError> {
Regex::builder().build_many(patterns)
}
/// Return a default configuration for a `Regex`.
///
/// This is a convenience routine to avoid needing to import the [`Config`]
/// type when customizing the construction of a `Regex`.
///
/// # Example: lower the NFA size limit
///
/// In some cases, the default size limit might be too big. The size limit
/// can be lowered, which will prevent large regex patterns from compiling.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::meta::Regex;
///
/// let result = Regex::builder()
/// .configure(Regex::config().nfa_size_limit(Some(20 * (1<<10))))
/// // Not even 20KB is enough to build a single large Unicode class!
/// .build(r"\pL");
/// assert!(result.is_err());
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn config() -> Config {
Config::new()
}
/// Return a builder for configuring the construction of a `Regex`.
///
/// This is a convenience routine to avoid needing to import the
/// [`Builder`] type in common cases.
///
/// # Example: change the line terminator
///
/// This example shows how to enable multi-line mode by default and change
/// the line terminator to the NUL byte:
///
/// ```
/// use regex_automata::{meta::Regex, util::syntax, Match};
///
/// let re = Regex::builder()
/// .syntax(syntax::Config::new().multi_line(true))
/// .configure(Regex::config().line_terminator(b'\x00'))
/// .build(r"^foo$")?;
/// let hay = "\x00foo\x00";
/// assert_eq!(Some(Match::must(0, 1..4)), re.find(hay));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn builder() -> Builder {
Builder::new()
}
}
/// High level convenience routines for using a regex to search a haystack.
impl Regex {
/// Returns true if and only if this regex matches the given haystack.
///
/// This routine may short circuit if it knows that scanning future input
/// will never lead to a different result. (Consider how this might make
/// a difference given the regex `a+` on the haystack `aaaaaaaaaaaaaaa`.
/// This routine _may_ stop after it sees the first `a`, but routines like
/// `find` need to continue searching because `+` is greedy by default.)
///
/// # Example
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new("foo[0-9]+bar")?;
///
/// assert!(re.is_match("foo12345bar"));
/// assert!(!re.is_match("foobar"));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: consistency with search APIs
///
/// `is_match` is guaranteed to return `true` whenever `find` returns a
/// match. This includes searches that are executed entirely within a
/// codepoint:
///
/// ```
/// use regex_automata::{meta::Regex, Input};
///
/// let re = Regex::new("a*")?;
///
/// // This doesn't match because the default configuration bans empty
/// // matches from splitting a codepoint.
/// assert!(!re.is_match(Input::new("☃").span(1..2)));
/// assert_eq!(None, re.find(Input::new("☃").span(1..2)));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// Notice that when UTF-8 mode is disabled, then the above reports a
/// match because the restriction against zero-width matches that split a
/// codepoint has been lifted:
///
/// ```
/// use regex_automata::{meta::Regex, Input, Match};
///
/// let re = Regex::builder()
/// .configure(Regex::config().utf8_empty(false))
/// .build("a*")?;
///
/// assert!(re.is_match(Input::new("☃").span(1..2)));
/// assert_eq!(
/// Some(Match::must(0, 1..1)),
/// re.find(Input::new("☃").span(1..2)),
/// );
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// A similar idea applies when using line anchors with CRLF mode enabled,
/// which prevents them from matching between a `\r` and a `\n`.
///
/// ```
/// use regex_automata::{meta::Regex, Input, Match};
///
/// let re = Regex::new(r"(?Rm:$)")?;
/// assert!(!re.is_match(Input::new("\r\n").span(1..1)));
/// // A regular line anchor, which only considers \n as a
/// // line terminator, will match.
/// let re = Regex::new(r"(?m:$)")?;
/// assert!(re.is_match(Input::new("\r\n").span(1..1)));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn is_match<'h, I: Into<Input<'h>>>(&self, input: I) -> bool {
let input = input.into().earliest(true);
if self.imp.info.is_impossible(&input) {
return false;
}
let mut guard = self.pool.get();
let result = self.imp.strat.is_match(&mut guard, &input);
// See 'Regex::search' for why we put the guard back explicitly.
PoolGuard::put(guard);
result
}
/// Executes a leftmost search and returns the first match that is found,
/// if one exists.
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Match};
///
/// let re = Regex::new("foo[0-9]+")?;
/// assert_eq!(Some(Match::must(0, 0..8)), re.find("foo12345"));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn find<'h, I: Into<Input<'h>>>(&self, input: I) -> Option<Match> {
self.search(&input.into())
}
/// Executes a leftmost forward search and writes the spans of capturing
/// groups that participated in a match into the provided [`Captures`]
/// value. If no match was found, then [`Captures::is_match`] is guaranteed
/// to return `false`.
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Span};
///
/// let re = Regex::new(r"^([0-9]{4})-([0-9]{2})-([0-9]{2})$")?;
/// let mut caps = re.create_captures();
///
/// re.captures("2010-03-14", &mut caps);
/// assert!(caps.is_match());
/// assert_eq!(Some(Span::from(0..4)), caps.get_group(1));
/// assert_eq!(Some(Span::from(5..7)), caps.get_group(2));
/// assert_eq!(Some(Span::from(8..10)), caps.get_group(3));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn captures<'h, I: Into<Input<'h>>>(
&self,
input: I,
caps: &mut Captures,
) {
self.search_captures(&input.into(), caps)
}
/// Returns an iterator over all non-overlapping leftmost matches in
/// the given haystack. If no match exists, then the iterator yields no
/// elements.
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Match};
///
/// let re = Regex::new("foo[0-9]+")?;
/// let haystack = "foo1 foo12 foo123";
/// let matches: Vec<Match> = re.find_iter(haystack).collect();
/// assert_eq!(matches, vec![
/// Match::must(0, 0..4),
/// Match::must(0, 5..10),
/// Match::must(0, 11..17),
/// ]);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn find_iter<'r, 'h, I: Into<Input<'h>>>(
&'r self,
input: I,
) -> FindMatches<'r, 'h> {
let cache = self.pool.get();
let it = iter::Searcher::new(input.into());
FindMatches { re: self, cache, it }
}
/// Returns an iterator over all non-overlapping `Captures` values. If no
/// match exists, then the iterator yields no elements.
///
/// This yields the same matches as [`Regex::find_iter`], but it includes
/// the spans of all capturing groups that participate in each match.
///
/// **Tip:** See [`util::iter::Searcher`](crate::util::iter::Searcher) for
/// how to correctly iterate over all matches in a haystack while avoiding
/// the creation of a new `Captures` value for every match. (Which you are
/// forced to do with an `Iterator`.)
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Span};
///
/// let re = Regex::new("foo(?P<numbers>[0-9]+)")?;
///
/// let haystack = "foo1 foo12 foo123";
/// let matches: Vec<Span> = re
/// .captures_iter(haystack)
/// // The unwrap is OK since 'numbers' matches if the pattern matches.
/// .map(|caps| caps.get_group_by_name("numbers").unwrap())
/// .collect();
/// assert_eq!(matches, vec![
/// Span::from(3..4),
/// Span::from(8..10),
/// Span::from(14..17),
/// ]);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn captures_iter<'r, 'h, I: Into<Input<'h>>>(
&'r self,
input: I,
) -> CapturesMatches<'r, 'h> {
let cache = self.pool.get();
let caps = self.create_captures();
let it = iter::Searcher::new(input.into());
CapturesMatches { re: self, cache, caps, it }
}
/// Returns an iterator of spans of the haystack given, delimited by a
/// match of the regex. Namely, each element of the iterator corresponds to
/// a part of the haystack that *isn't* matched by the regular expression.
///
/// # Example
///
/// To split a string delimited by arbitrary amounts of spaces or tabs:
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r"[ \t]+")?;
/// let hay = "a b \t c\td e";
/// let fields: Vec<&str> = re.split(hay).map(|span| &hay[span]).collect();
/// assert_eq!(fields, vec!["a", "b", "c", "d", "e"]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: more cases
///
/// Basic usage:
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r" ")?;
/// let hay = "Mary had a little lamb";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["Mary", "had", "a", "little", "lamb"]);
///
/// let re = Regex::new(r"X")?;
/// let hay = "";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec![""]);
///
/// let re = Regex::new(r"X")?;
/// let hay = "lionXXtigerXleopard";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["lion", "", "tiger", "leopard"]);
///
/// let re = Regex::new(r"::")?;
/// let hay = "lion::tiger::leopard";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["lion", "tiger", "leopard"]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// If a haystack contains multiple contiguous matches, you will end up
/// with empty spans yielded by the iterator:
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r"X")?;
/// let hay = "XXXXaXXbXc";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["", "", "", "", "a", "", "b", "c"]);
///
/// let re = Regex::new(r"/")?;
/// let hay = "(///)";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["(", "", "", ")"]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// Separators at the start or end of a haystack are neighbored by empty
/// spans.
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r"0")?;
/// let hay = "010";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["", "1", ""]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// When the empty string is used as a regex, it splits at every valid
/// UTF-8 boundary by default (which includes the beginning and end of the
/// haystack):
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r"")?;
/// let hay = "rust";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["", "r", "u", "s", "t", ""]);
///
/// // Splitting by an empty string is UTF-8 aware by default!
/// let re = Regex::new(r"")?;
/// let hay = "☃";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["", "☃", ""]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// But note that UTF-8 mode for empty strings can be disabled, which will
/// then result in a match at every byte offset in the haystack,
/// including between every UTF-8 code unit.
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::builder()
/// .configure(Regex::config().utf8_empty(false))
/// .build(r"")?;
/// let hay = "☃".as_bytes();
/// let got: Vec<&[u8]> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec![
/// // Writing byte string slices is just brutal. The problem is that
/// // b"foo" has type &[u8; 3] instead of &[u8].
/// &[][..], &[b'\xE2'][..], &[b'\x98'][..], &[b'\x83'][..], &[][..],
/// ]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// Contiguous separators (commonly shows up with whitespace), can lead to
/// possibly surprising behavior. For example, this code is correct:
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r" ")?;
/// let hay = " a b c";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["", "", "", "", "a", "", "b", "c"]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// It does *not* give you `["a", "b", "c"]`. For that behavior, you'd want
/// to match contiguous space characters:
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r" +")?;
/// let hay = " a b c";
/// let got: Vec<&str> = re.split(hay).map(|sp| &hay[sp]).collect();
/// // N.B. This does still include a leading empty span because ' +'
/// // matches at the beginning of the haystack.
/// assert_eq!(got, vec!["", "a", "b", "c"]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn split<'r, 'h, I: Into<Input<'h>>>(
&'r self,
input: I,
) -> Split<'r, 'h> {
Split { finder: self.find_iter(input), last: 0 }
}
/// Returns an iterator of at most `limit` spans of the haystack given,
/// delimited by a match of the regex. (A `limit` of `0` will return no
/// spans.) Namely, each element of the iterator corresponds to a part
/// of the haystack that *isn't* matched by the regular expression. The
/// remainder of the haystack that is not split will be the last element in
/// the iterator.
///
/// # Example
///
/// Get the first two words in some haystack:
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r"\W+").unwrap();
/// let hay = "Hey! How are you?";
/// let fields: Vec<&str> =
/// re.splitn(hay, 3).map(|span| &hay[span]).collect();
/// assert_eq!(fields, vec!["Hey", "How", "are you?"]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Examples: more cases
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r" ")?;
/// let hay = "Mary had a little lamb";
/// let got: Vec<&str> = re.splitn(hay, 3).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["Mary", "had", "a little lamb"]);
///
/// let re = Regex::new(r"X")?;
/// let hay = "";
/// let got: Vec<&str> = re.splitn(hay, 3).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec![""]);
///
/// let re = Regex::new(r"X")?;
/// let hay = "lionXXtigerXleopard";
/// let got: Vec<&str> = re.splitn(hay, 3).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["lion", "", "tigerXleopard"]);
///
/// let re = Regex::new(r"::")?;
/// let hay = "lion::tiger::leopard";
/// let got: Vec<&str> = re.splitn(hay, 2).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["lion", "tiger::leopard"]);
///
/// let re = Regex::new(r"X")?;
/// let hay = "abcXdef";
/// let got: Vec<&str> = re.splitn(hay, 1).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["abcXdef"]);
///
/// let re = Regex::new(r"X")?;
/// let hay = "abcdef";
/// let got: Vec<&str> = re.splitn(hay, 2).map(|sp| &hay[sp]).collect();
/// assert_eq!(got, vec!["abcdef"]);
///
/// let re = Regex::new(r"X")?;
/// let hay = "abcXdef";
/// let got: Vec<&str> = re.splitn(hay, 0).map(|sp| &hay[sp]).collect();
/// assert!(got.is_empty());
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn splitn<'r, 'h, I: Into<Input<'h>>>(
&'r self,
input: I,
limit: usize,
) -> SplitN<'r, 'h> {
SplitN { splits: self.split(input), limit }
}
}
/// Lower level search routines that give more control.
impl Regex {
/// Returns the start and end offset of the leftmost match. If no match
/// exists, then `None` is returned.
///
/// This is like [`Regex::find`] but, but it accepts a concrete `&Input`
/// instead of an `Into<Input>`.
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Input, Match};
///
/// let re = Regex::new(r"Samwise|Sam")?;
/// let input = Input::new(
/// "one of the chief characters, Samwise the Brave",
/// );
/// assert_eq!(Some(Match::must(0, 29..36)), re.search(&input));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn search(&self, input: &Input<'_>) -> Option<Match> {
if self.imp.info.is_impossible(input) {
return None;
}
let mut guard = self.pool.get();
let result = self.imp.strat.search(&mut guard, input);
// We do this dance with the guard and explicitly put it back in the
// pool because it seems to result in better codegen. If we let the
// guard's Drop impl put it back in the pool, then functions like
// ptr::drop_in_place get called and they *don't* get inlined. This
// isn't usually a big deal, but in latency sensitive benchmarks the
// extra function call can matter.
//
// I used `rebar measure -f '^grep/every-line$' -e meta` to measure
// the effects here.
//
// Note that this doesn't eliminate the latency effects of using the
// pool. There is still some (minor) cost for the "thread owner" of the
// pool. (i.e., The thread that first calls a regex search routine.)
// However, for other threads using the regex, the pool access can be
// quite expensive as it goes through a mutex. Callers can avoid this
// by either cloning the Regex (which creates a distinct copy of the
// pool), or callers can use the lower level APIs that accept a 'Cache'
// directly and do their own handling.
PoolGuard::put(guard);
result
}
/// Returns the end offset of the leftmost match. If no match exists, then
/// `None` is returned.
///
/// This is distinct from [`Regex::search`] in that it only returns the end
/// of a match and not the start of the match. Depending on a variety of
/// implementation details, this _may_ permit the regex engine to do less
/// overall work. For example, if a DFA is being used to execute a search,
/// then the start of a match usually requires running a separate DFA in
/// reverse to the find the start of a match. If one only needs the end of
/// a match, then the separate reverse scan to find the start of a match
/// can be skipped. (Note that the reverse scan is avoided even when using
/// `Regex::search` when possible, for example, in the case of an anchored
/// search.)
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Input, HalfMatch};
///
/// let re = Regex::new(r"Samwise|Sam")?;
/// let input = Input::new(
/// "one of the chief characters, Samwise the Brave",
/// );
/// assert_eq!(Some(HalfMatch::must(0, 36)), re.search_half(&input));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn search_half(&self, input: &Input<'_>) -> Option<HalfMatch> {
if self.imp.info.is_impossible(input) {
return None;
}
let mut guard = self.pool.get();
let result = self.imp.strat.search_half(&mut guard, input);
// See 'Regex::search' for why we put the guard back explicitly.
PoolGuard::put(guard);
result
}
/// Executes a leftmost forward search and writes the spans of capturing
/// groups that participated in a match into the provided [`Captures`]
/// value. If no match was found, then [`Captures::is_match`] is guaranteed
/// to return `false`.
///
/// This is like [`Regex::captures`], but it accepts a concrete `&Input`
/// instead of an `Into<Input>`.
///
/// # Example: specific pattern search
///
/// This example shows how to build a multi-pattern `Regex` that permits
/// searching for specific patterns.
///
/// ```
/// use regex_automata::{
/// meta::Regex,
/// Anchored, Match, PatternID, Input,
/// };
///
/// let re = Regex::new_many(&["[a-z0-9]{6}", "[a-z][a-z0-9]{5}"])?;
/// let mut caps = re.create_captures();
/// let haystack = "foo123";
///
/// // Since we are using the default leftmost-first match and both
/// // patterns match at the same starting position, only the first pattern
/// // will be returned in this case when doing a search for any of the
/// // patterns.
/// let expected = Some(Match::must(0, 0..6));
/// re.search_captures(&Input::new(haystack), &mut caps);
/// assert_eq!(expected, caps.get_match());
///
/// // But if we want to check whether some other pattern matches, then we
/// // can provide its pattern ID.
/// let expected = Some(Match::must(1, 0..6));
/// let input = Input::new(haystack)
/// .anchored(Anchored::Pattern(PatternID::must(1)));
/// re.search_captures(&input, &mut caps);
/// assert_eq!(expected, caps.get_match());
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: specifying the bounds of a search
///
/// This example shows how providing the bounds of a search can produce
/// different results than simply sub-slicing the haystack.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{meta::Regex, Match, Input};
///
/// let re = Regex::new(r"\b[0-9]{3}\b")?;
/// let mut caps = re.create_captures();
/// let haystack = "foo123bar";
///
/// // Since we sub-slice the haystack, the search doesn't know about
/// // the larger context and assumes that `123` is surrounded by word
/// // boundaries. And of course, the match position is reported relative
/// // to the sub-slice as well, which means we get `0..3` instead of
/// // `3..6`.
/// let expected = Some(Match::must(0, 0..3));
/// let input = Input::new(&haystack[3..6]);
/// re.search_captures(&input, &mut caps);
/// assert_eq!(expected, caps.get_match());
///
/// // But if we provide the bounds of the search within the context of the
/// // entire haystack, then the search can take the surrounding context
/// // into account. (And if we did find a match, it would be reported
/// // as a valid offset into `haystack` instead of its sub-slice.)
/// let expected = None;
/// let input = Input::new(haystack).range(3..6);
/// re.search_captures(&input, &mut caps);
/// assert_eq!(expected, caps.get_match());
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn search_captures(&self, input: &Input<'_>, caps: &mut Captures) {
caps.set_pattern(None);
let pid = self.search_slots(input, caps.slots_mut());
caps.set_pattern(pid);
}
/// Executes a leftmost forward search and writes the spans of capturing
/// groups that participated in a match into the provided `slots`, and
/// returns the matching pattern ID. The contents of the slots for patterns
/// other than the matching pattern are unspecified. If no match was found,
/// then `None` is returned and the contents of `slots` is unspecified.
///
/// This is like [`Regex::search`], but it accepts a raw slots slice
/// instead of a `Captures` value. This is useful in contexts where you
/// don't want or need to allocate a `Captures`.
///
/// It is legal to pass _any_ number of slots to this routine. If the regex
/// engine would otherwise write a slot offset that doesn't fit in the
/// provided slice, then it is simply skipped. In general though, there are
/// usually three slice lengths you might want to use:
///
/// * An empty slice, if you only care about which pattern matched.
/// * A slice with [`pattern_len() * 2`](Regex::pattern_len) slots, if you
/// only care about the overall match spans for each matching pattern.
/// * A slice with
/// [`slot_len()`](crate::util::captures::GroupInfo::slot_len) slots, which
/// permits recording match offsets for every capturing group in every
/// pattern.
///
/// # Example
///
/// This example shows how to find the overall match offsets in a
/// multi-pattern search without allocating a `Captures` value. Indeed, we
/// can put our slots right on the stack.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{meta::Regex, PatternID, Input};
///
/// let re = Regex::new_many(&[
/// r"\pL+",
/// r"\d+",
/// ])?;
/// let input = Input::new("!@#123");
///
/// // We only care about the overall match offsets here, so we just
/// // allocate two slots for each pattern. Each slot records the start
/// // and end of the match.
/// let mut slots = [None; 4];
/// let pid = re.search_slots(&input, &mut slots);
/// assert_eq!(Some(PatternID::must(1)), pid);
///
/// // The overall match offsets are always at 'pid * 2' and 'pid * 2 + 1'.
/// // See 'GroupInfo' for more details on the mapping between groups and
/// // slot indices.
/// let slot_start = pid.unwrap().as_usize() * 2;
/// let slot_end = slot_start + 1;
/// assert_eq!(Some(3), slots[slot_start].map(|s| s.get()));
/// assert_eq!(Some(6), slots[slot_end].map(|s| s.get()));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn search_slots(
&self,
input: &Input<'_>,
slots: &mut [Option<NonMaxUsize>],
) -> Option<PatternID> {
if self.imp.info.is_impossible(input) {
return None;
}
let mut guard = self.pool.get();
let result = self.imp.strat.search_slots(&mut guard, input, slots);
// See 'Regex::search' for why we put the guard back explicitly.
PoolGuard::put(guard);
result
}
/// Writes the set of patterns that match anywhere in the given search
/// configuration to `patset`. If multiple patterns match at the same
/// position and this `Regex` was configured with [`MatchKind::All`]
/// semantics, then all matching patterns are written to the given set.
///
/// Unless all of the patterns in this `Regex` are anchored, then generally
/// speaking, this will scan the entire haystack.
///
/// This search routine *does not* clear the pattern set. This gives some
/// flexibility to the caller (e.g., running multiple searches with the
/// same pattern set), but does make the API bug-prone if you're reusing
/// the same pattern set for multiple searches but intended them to be
/// independent.
///
/// If a pattern ID matched but the given `PatternSet` does not have
/// sufficient capacity to store it, then it is not inserted and silently
/// dropped.
///
/// # Example
///
/// This example shows how to find all matching patterns in a haystack,
/// even when some patterns match at the same position as other patterns.
/// It is important that we configure the `Regex` with [`MatchKind::All`]
/// semantics here, or else overlapping matches will not be reported.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{meta::Regex, Input, MatchKind, PatternSet};
///
/// let patterns = &[
/// r"\w+", r"\d+", r"\pL+", r"foo", r"bar", r"barfoo", r"foobar",
/// ];
/// let re = Regex::builder()
/// .configure(Regex::config().match_kind(MatchKind::All))
/// .build_many(patterns)?;
///
/// let input = Input::new("foobar");
/// let mut patset = PatternSet::new(re.pattern_len());
/// re.which_overlapping_matches(&input, &mut patset);
/// let expected = vec![0, 2, 3, 4, 6];
/// let got: Vec<usize> = patset.iter().map(|p| p.as_usize()).collect();
/// assert_eq!(expected, got);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn which_overlapping_matches(
&self,
input: &Input<'_>,
patset: &mut PatternSet,
) {
if self.imp.info.is_impossible(input) {
return;
}
let mut guard = self.pool.get();
let result = self
.imp
.strat
.which_overlapping_matches(&mut guard, input, patset);
// See 'Regex::search' for why we put the guard back explicitly.
PoolGuard::put(guard);
result
}
}
/// Lower level search routines that give more control, and require the caller
/// to provide an explicit [`Cache`] parameter.
impl Regex {
/// This is like [`Regex::search`], but requires the caller to
/// explicitly pass a [`Cache`].
///
/// # Why pass a `Cache` explicitly?
///
/// Passing a `Cache` explicitly will bypass the use of an internal memory
/// pool used by `Regex` to get a `Cache` for a search. The use of this
/// pool can be slower in some cases when a `Regex` is used from multiple
/// threads simultaneously. Typically, performance only becomes an issue
/// when there is heavy contention, which in turn usually only occurs
/// when each thread's primary unit of work is a regex search on a small
/// haystack.
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Input, Match};
///
/// let re = Regex::new(r"Samwise|Sam")?;
/// let mut cache = re.create_cache();
/// let input = Input::new(
/// "one of the chief characters, Samwise the Brave",
/// );
/// assert_eq!(
/// Some(Match::must(0, 29..36)),
/// re.search_with(&mut cache, &input),
/// );
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn search_with(
&self,
cache: &mut Cache,
input: &Input<'_>,
) -> Option<Match> {
if self.imp.info.is_impossible(input) {
return None;
}
self.imp.strat.search(cache, input)
}
/// This is like [`Regex::search_half`], but requires the caller to
/// explicitly pass a [`Cache`].
///
/// # Why pass a `Cache` explicitly?
///
/// Passing a `Cache` explicitly will bypass the use of an internal memory
/// pool used by `Regex` to get a `Cache` for a search. The use of this
/// pool can be slower in some cases when a `Regex` is used from multiple
/// threads simultaneously. Typically, performance only becomes an issue
/// when there is heavy contention, which in turn usually only occurs
/// when each thread's primary unit of work is a regex search on a small
/// haystack.
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Input, HalfMatch};
///
/// let re = Regex::new(r"Samwise|Sam")?;
/// let mut cache = re.create_cache();
/// let input = Input::new(
/// "one of the chief characters, Samwise the Brave",
/// );
/// assert_eq!(
/// Some(HalfMatch::must(0, 36)),
/// re.search_half_with(&mut cache, &input),
/// );
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn search_half_with(
&self,
cache: &mut Cache,
input: &Input<'_>,
) -> Option<HalfMatch> {
if self.imp.info.is_impossible(input) {
return None;
}
self.imp.strat.search_half(cache, input)
}
/// This is like [`Regex::search_captures`], but requires the caller to
/// explicitly pass a [`Cache`].
///
/// # Why pass a `Cache` explicitly?
///
/// Passing a `Cache` explicitly will bypass the use of an internal memory
/// pool used by `Regex` to get a `Cache` for a search. The use of this
/// pool can be slower in some cases when a `Regex` is used from multiple
/// threads simultaneously. Typically, performance only becomes an issue
/// when there is heavy contention, which in turn usually only occurs
/// when each thread's primary unit of work is a regex search on a small
/// haystack.
///
/// # Example: specific pattern search
///
/// This example shows how to build a multi-pattern `Regex` that permits
/// searching for specific patterns.
///
/// ```
/// use regex_automata::{
/// meta::Regex,
/// Anchored, Match, PatternID, Input,
/// };
///
/// let re = Regex::new_many(&["[a-z0-9]{6}", "[a-z][a-z0-9]{5}"])?;
/// let (mut cache, mut caps) = (re.create_cache(), re.create_captures());
/// let haystack = "foo123";
///
/// // Since we are using the default leftmost-first match and both
/// // patterns match at the same starting position, only the first pattern
/// // will be returned in this case when doing a search for any of the
/// // patterns.
/// let expected = Some(Match::must(0, 0..6));
/// re.search_captures_with(&mut cache, &Input::new(haystack), &mut caps);
/// assert_eq!(expected, caps.get_match());
///
/// // But if we want to check whether some other pattern matches, then we
/// // can provide its pattern ID.
/// let expected = Some(Match::must(1, 0..6));
/// let input = Input::new(haystack)
/// .anchored(Anchored::Pattern(PatternID::must(1)));
/// re.search_captures_with(&mut cache, &input, &mut caps);
/// assert_eq!(expected, caps.get_match());
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: specifying the bounds of a search
///
/// This example shows how providing the bounds of a search can produce
/// different results than simply sub-slicing the haystack.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{meta::Regex, Match, Input};
///
/// let re = Regex::new(r"\b[0-9]{3}\b")?;
/// let (mut cache, mut caps) = (re.create_cache(), re.create_captures());
/// let haystack = "foo123bar";
///
/// // Since we sub-slice the haystack, the search doesn't know about
/// // the larger context and assumes that `123` is surrounded by word
/// // boundaries. And of course, the match position is reported relative
/// // to the sub-slice as well, which means we get `0..3` instead of
/// // `3..6`.
/// let expected = Some(Match::must(0, 0..3));
/// let input = Input::new(&haystack[3..6]);
/// re.search_captures_with(&mut cache, &input, &mut caps);
/// assert_eq!(expected, caps.get_match());
///
/// // But if we provide the bounds of the search within the context of the
/// // entire haystack, then the search can take the surrounding context
/// // into account. (And if we did find a match, it would be reported
/// // as a valid offset into `haystack` instead of its sub-slice.)
/// let expected = None;
/// let input = Input::new(haystack).range(3..6);
/// re.search_captures_with(&mut cache, &input, &mut caps);
/// assert_eq!(expected, caps.get_match());
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn search_captures_with(
&self,
cache: &mut Cache,
input: &Input<'_>,
caps: &mut Captures,
) {
caps.set_pattern(None);
let pid = self.search_slots_with(cache, input, caps.slots_mut());
caps.set_pattern(pid);
}
/// This is like [`Regex::search_slots`], but requires the caller to
/// explicitly pass a [`Cache`].
///
/// # Why pass a `Cache` explicitly?
///
/// Passing a `Cache` explicitly will bypass the use of an internal memory
/// pool used by `Regex` to get a `Cache` for a search. The use of this
/// pool can be slower in some cases when a `Regex` is used from multiple
/// threads simultaneously. Typically, performance only becomes an issue
/// when there is heavy contention, which in turn usually only occurs
/// when each thread's primary unit of work is a regex search on a small
/// haystack.
///
/// # Example
///
/// This example shows how to find the overall match offsets in a
/// multi-pattern search without allocating a `Captures` value. Indeed, we
/// can put our slots right on the stack.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{meta::Regex, PatternID, Input};
///
/// let re = Regex::new_many(&[
/// r"\pL+",
/// r"\d+",
/// ])?;
/// let mut cache = re.create_cache();
/// let input = Input::new("!@#123");
///
/// // We only care about the overall match offsets here, so we just
/// // allocate two slots for each pattern. Each slot records the start
/// // and end of the match.
/// let mut slots = [None; 4];
/// let pid = re.search_slots_with(&mut cache, &input, &mut slots);
/// assert_eq!(Some(PatternID::must(1)), pid);
///
/// // The overall match offsets are always at 'pid * 2' and 'pid * 2 + 1'.
/// // See 'GroupInfo' for more details on the mapping between groups and
/// // slot indices.
/// let slot_start = pid.unwrap().as_usize() * 2;
/// let slot_end = slot_start + 1;
/// assert_eq!(Some(3), slots[slot_start].map(|s| s.get()));
/// assert_eq!(Some(6), slots[slot_end].map(|s| s.get()));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn search_slots_with(
&self,
cache: &mut Cache,
input: &Input<'_>,
slots: &mut [Option<NonMaxUsize>],
) -> Option<PatternID> {
if self.imp.info.is_impossible(input) {
return None;
}
self.imp.strat.search_slots(cache, input, slots)
}
/// This is like [`Regex::which_overlapping_matches`], but requires the
/// caller to explicitly pass a [`Cache`].
///
/// Passing a `Cache` explicitly will bypass the use of an internal memory
/// pool used by `Regex` to get a `Cache` for a search. The use of this
/// pool can be slower in some cases when a `Regex` is used from multiple
/// threads simultaneously. Typically, performance only becomes an issue
/// when there is heavy contention, which in turn usually only occurs
/// when each thread's primary unit of work is a regex search on a small
/// haystack.
///
/// # Why pass a `Cache` explicitly?
///
/// # Example
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{meta::Regex, Input, MatchKind, PatternSet};
///
/// let patterns = &[
/// r"\w+", r"\d+", r"\pL+", r"foo", r"bar", r"barfoo", r"foobar",
/// ];
/// let re = Regex::builder()
/// .configure(Regex::config().match_kind(MatchKind::All))
/// .build_many(patterns)?;
/// let mut cache = re.create_cache();
///
/// let input = Input::new("foobar");
/// let mut patset = PatternSet::new(re.pattern_len());
/// re.which_overlapping_matches_with(&mut cache, &input, &mut patset);
/// let expected = vec![0, 2, 3, 4, 6];
/// let got: Vec<usize> = patset.iter().map(|p| p.as_usize()).collect();
/// assert_eq!(expected, got);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn which_overlapping_matches_with(
&self,
cache: &mut Cache,
input: &Input<'_>,
patset: &mut PatternSet,
) {
if self.imp.info.is_impossible(input) {
return;
}
self.imp.strat.which_overlapping_matches(cache, input, patset)
}
}
/// Various non-search routines for querying properties of a `Regex` and
/// convenience routines for creating [`Captures`] and [`Cache`] values.
impl Regex {
/// Creates a new object for recording capture group offsets. This is used
/// in search APIs like [`Regex::captures`] and [`Regex::search_captures`].
///
/// This is a convenience routine for
/// `Captures::all(re.group_info().clone())`. Callers may build other types
/// of `Captures` values that record less information (and thus require
/// less work from the regex engine) using [`Captures::matches`] and
/// [`Captures::empty`].
///
/// # Example
///
/// This shows some alternatives to [`Regex::create_captures`]:
///
/// ```
/// use regex_automata::{
/// meta::Regex,
/// util::captures::Captures,
/// Match, PatternID, Span,
/// };
///
/// let re = Regex::new(r"(?<first>[A-Z][a-z]+) (?<last>[A-Z][a-z]+)")?;
///
/// // This is equivalent to Regex::create_captures. It stores matching
/// // offsets for all groups in the regex.
/// let mut all = Captures::all(re.group_info().clone());
/// re.captures("Bruce Springsteen", &mut all);
/// assert_eq!(Some(Match::must(0, 0..17)), all.get_match());
/// assert_eq!(Some(Span::from(0..5)), all.get_group_by_name("first"));
/// assert_eq!(Some(Span::from(6..17)), all.get_group_by_name("last"));
///
/// // In this version, we only care about the implicit groups, which
/// // means offsets for the explicit groups will be unavailable. It can
/// // sometimes be faster to ask for fewer groups, since the underlying
/// // regex engine needs to do less work to keep track of them.
/// let mut matches = Captures::matches(re.group_info().clone());
/// re.captures("Bruce Springsteen", &mut matches);
/// // We still get the overall match info.
/// assert_eq!(Some(Match::must(0, 0..17)), matches.get_match());
/// // But now the explicit groups are unavailable.
/// assert_eq!(None, matches.get_group_by_name("first"));
/// assert_eq!(None, matches.get_group_by_name("last"));
///
/// // Finally, in this version, we don't ask to keep track of offsets for
/// // *any* groups. All we get back is whether a match occurred, and if
/// // so, the ID of the pattern that matched.
/// let mut empty = Captures::empty(re.group_info().clone());
/// re.captures("Bruce Springsteen", &mut empty);
/// // it's a match!
/// assert!(empty.is_match());
/// // for pattern ID 0
/// assert_eq!(Some(PatternID::ZERO), empty.pattern());
/// // Match offsets are unavailable.
/// assert_eq!(None, empty.get_match());
/// // And of course, explicit groups are unavailable too.
/// assert_eq!(None, empty.get_group_by_name("first"));
/// assert_eq!(None, empty.get_group_by_name("last"));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn create_captures(&self) -> Captures {
Captures::all(self.group_info().clone())
}
/// Creates a new cache for use with lower level search APIs like
/// [`Regex::search_with`].
///
/// The cache returned should only be used for searches for this `Regex`.
/// If you want to reuse the cache for another `Regex`, then you must call
/// [`Cache::reset`] with that `Regex`.
///
/// This is a convenience routine for [`Cache::new`].
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Input, Match};
///
/// let re = Regex::new(r"(?-u)m\w+\s+m\w+")?;
/// let mut cache = re.create_cache();
/// let input = Input::new("crazy janey and her mission man");
/// assert_eq!(
/// Some(Match::must(0, 20..31)),
/// re.search_with(&mut cache, &input),
/// );
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn create_cache(&self) -> Cache {
self.imp.strat.create_cache()
}
/// Returns the total number of patterns in this regex.
///
/// The standard [`Regex::new`] constructor always results in a `Regex`
/// with a single pattern, but [`Regex::new_many`] permits building a
/// multi-pattern regex.
///
/// A `Regex` guarantees that the maximum possible `PatternID` returned in
/// any match is `Regex::pattern_len() - 1`. In the case where the number
/// of patterns is `0`, a match is impossible.
///
/// # Example
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let re = Regex::new(r"(?m)^[a-z]$")?;
/// assert_eq!(1, re.pattern_len());
///
/// let re = Regex::new_many::<&str>(&[])?;
/// assert_eq!(0, re.pattern_len());
///
/// let re = Regex::new_many(&["a", "b", "c"])?;
/// assert_eq!(3, re.pattern_len());
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn pattern_len(&self) -> usize {
self.imp.info.pattern_len()
}
/// Returns the total number of capturing groups.
///
/// This includes the implicit capturing group corresponding to the
/// entire match. Therefore, the minimum value returned is `1`.
///
/// # Example
///
/// This shows a few patterns and how many capture groups they have.
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let len = |pattern| {
/// Regex::new(pattern).map(|re| re.captures_len())
/// };
///
/// assert_eq!(1, len("a")?);
/// assert_eq!(2, len("(a)")?);
/// assert_eq!(3, len("(a)|(b)")?);
/// assert_eq!(5, len("(a)(b)|(c)(d)")?);
/// assert_eq!(2, len("(a)|b")?);
/// assert_eq!(2, len("a|(b)")?);
/// assert_eq!(2, len("(b)*")?);
/// assert_eq!(2, len("(b)+")?);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: multiple patterns
///
/// This routine also works for multiple patterns. The total number is
/// the sum of the capture groups of each pattern.
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let len = |patterns| {
/// Regex::new_many(patterns).map(|re| re.captures_len())
/// };
///
/// assert_eq!(2, len(&["a", "b"])?);
/// assert_eq!(4, len(&["(a)", "(b)"])?);
/// assert_eq!(6, len(&["(a)|(b)", "(c)|(d)"])?);
/// assert_eq!(8, len(&["(a)(b)|(c)(d)", "(x)(y)"])?);
/// assert_eq!(3, len(&["(a)", "b"])?);
/// assert_eq!(3, len(&["a", "(b)"])?);
/// assert_eq!(4, len(&["(a)", "(b)*"])?);
/// assert_eq!(4, len(&["(a)+", "(b)+"])?);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn captures_len(&self) -> usize {
self.imp
.info
.props_union()
.explicit_captures_len()
.saturating_add(self.pattern_len())
}
/// Returns the total number of capturing groups that appear in every
/// possible match.
///
/// If the number of capture groups can vary depending on the match, then
/// this returns `None`. That is, a value is only returned when the number
/// of matching groups is invariant or "static."
///
/// Note that like [`Regex::captures_len`], this **does** include the
/// implicit capturing group corresponding to the entire match. Therefore,
/// when a non-None value is returned, it is guaranteed to be at least `1`.
/// Stated differently, a return value of `Some(0)` is impossible.
///
/// # Example
///
/// This shows a few cases where a static number of capture groups is
/// available and a few cases where it is not.
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let len = |pattern| {
/// Regex::new(pattern).map(|re| re.static_captures_len())
/// };
///
/// assert_eq!(Some(1), len("a")?);
/// assert_eq!(Some(2), len("(a)")?);
/// assert_eq!(Some(2), len("(a)|(b)")?);
/// assert_eq!(Some(3), len("(a)(b)|(c)(d)")?);
/// assert_eq!(None, len("(a)|b")?);
/// assert_eq!(None, len("a|(b)")?);
/// assert_eq!(None, len("(b)*")?);
/// assert_eq!(Some(2), len("(b)+")?);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: multiple patterns
///
/// This property extends to regexes with multiple patterns as well. In
/// order for their to be a static number of capture groups in this case,
/// every pattern must have the same static number.
///
/// ```
/// use regex_automata::meta::Regex;
///
/// let len = |patterns| {
/// Regex::new_many(patterns).map(|re| re.static_captures_len())
/// };
///
/// assert_eq!(Some(1), len(&["a", "b"])?);
/// assert_eq!(Some(2), len(&["(a)", "(b)"])?);
/// assert_eq!(Some(2), len(&["(a)|(b)", "(c)|(d)"])?);
/// assert_eq!(Some(3), len(&["(a)(b)|(c)(d)", "(x)(y)"])?);
/// assert_eq!(None, len(&["(a)", "b"])?);
/// assert_eq!(None, len(&["a", "(b)"])?);
/// assert_eq!(None, len(&["(a)", "(b)*"])?);
/// assert_eq!(Some(2), len(&["(a)+", "(b)+"])?);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn static_captures_len(&self) -> Option<usize> {
self.imp
.info
.props_union()
.static_explicit_captures_len()
.map(|len| len.saturating_add(1))
}
/// Return information about the capture groups in this `Regex`.
///
/// A `GroupInfo` is an immutable object that can be cheaply cloned. It
/// is responsible for maintaining a mapping between the capture groups
/// in the concrete syntax of zero or more regex patterns and their
/// internal representation used by some of the regex matchers. It is also
/// responsible for maintaining a mapping between the name of each group
/// (if one exists) and its corresponding group index.
///
/// A `GroupInfo` is ultimately what is used to build a [`Captures`] value,
/// which is some mutable space where group offsets are stored as a result
/// of a search.
///
/// # Example
///
/// This shows some alternatives to [`Regex::create_captures`]:
///
/// ```
/// use regex_automata::{
/// meta::Regex,
/// util::captures::Captures,
/// Match, PatternID, Span,
/// };
///
/// let re = Regex::new(r"(?<first>[A-Z][a-z]+) (?<last>[A-Z][a-z]+)")?;
///
/// // This is equivalent to Regex::create_captures. It stores matching
/// // offsets for all groups in the regex.
/// let mut all = Captures::all(re.group_info().clone());
/// re.captures("Bruce Springsteen", &mut all);
/// assert_eq!(Some(Match::must(0, 0..17)), all.get_match());
/// assert_eq!(Some(Span::from(0..5)), all.get_group_by_name("first"));
/// assert_eq!(Some(Span::from(6..17)), all.get_group_by_name("last"));
///
/// // In this version, we only care about the implicit groups, which
/// // means offsets for the explicit groups will be unavailable. It can
/// // sometimes be faster to ask for fewer groups, since the underlying
/// // regex engine needs to do less work to keep track of them.
/// let mut matches = Captures::matches(re.group_info().clone());
/// re.captures("Bruce Springsteen", &mut matches);
/// // We still get the overall match info.
/// assert_eq!(Some(Match::must(0, 0..17)), matches.get_match());
/// // But now the explicit groups are unavailable.
/// assert_eq!(None, matches.get_group_by_name("first"));
/// assert_eq!(None, matches.get_group_by_name("last"));
///
/// // Finally, in this version, we don't ask to keep track of offsets for
/// // *any* groups. All we get back is whether a match occurred, and if
/// // so, the ID of the pattern that matched.
/// let mut empty = Captures::empty(re.group_info().clone());
/// re.captures("Bruce Springsteen", &mut empty);
/// // it's a match!
/// assert!(empty.is_match());
/// // for pattern ID 0
/// assert_eq!(Some(PatternID::ZERO), empty.pattern());
/// // Match offsets are unavailable.
/// assert_eq!(None, empty.get_match());
/// // And of course, explicit groups are unavailable too.
/// assert_eq!(None, empty.get_group_by_name("first"));
/// assert_eq!(None, empty.get_group_by_name("last"));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn group_info(&self) -> &GroupInfo {
self.imp.strat.group_info()
}
/// Returns the configuration object used to build this `Regex`.
///
/// If no configuration object was explicitly passed, then the
/// configuration returned represents the default.
#[inline]
pub fn get_config(&self) -> &Config {
self.imp.info.config()
}
/// Returns true if this regex has a high chance of being "accelerated."
///
/// The precise meaning of "accelerated" is specifically left unspecified,
/// but the general meaning is that the search is a high likelihood of
/// running faster than a character-at-a-time loop inside a standard
/// regex engine.
///
/// When a regex is accelerated, it is only a *probabilistic* claim. That
/// is, just because the regex is believed to be accelerated, that doesn't
/// mean it will definitely execute searches very fast. Similarly, if a
/// regex is *not* accelerated, that is also a probabilistic claim. That
/// is, a regex for which `is_accelerated` returns `false` could still run
/// searches more quickly than a regex for which `is_accelerated` returns
/// `true`.
///
/// Whether a regex is marked as accelerated or not is dependent on
/// implementations details that may change in a semver compatible release.
/// That is, a regex that is accelerated in a `x.y.1` release might not be
/// accelerated in a `x.y.2` release.
///
/// Basically, the value of acceleration boils down to a hedge: a hodge
/// podge of internal heuristics combine to make a probabilistic guess
/// that this regex search may run "fast." The value in knowing this from
/// a caller's perspective is that it may act as a signal that no further
/// work should be done to accelerate a search. For example, a grep-like
/// tool might try to do some extra work extracting literals from a regex
/// to create its own heuristic acceleration strategies. But it might
/// choose to defer to this crate's acceleration strategy if one exists.
/// This routine permits querying whether such a strategy is active for a
/// particular regex.
///
/// # Example
///
/// ```
/// use regex_automata::meta::Regex;
///
/// // A simple literal is very likely to be accelerated.
/// let re = Regex::new(r"foo")?;
/// assert!(re.is_accelerated());
///
/// // A regex with no literals is likely to not be accelerated.
/// let re = Regex::new(r"\w")?;
/// assert!(!re.is_accelerated());
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn is_accelerated(&self) -> bool {
self.imp.strat.is_accelerated()
}
/// Return the total approximate heap memory, in bytes, used by this `Regex`.
///
/// Note that currently, there is no high level configuration for setting
/// a limit on the specific value returned by this routine. Instead, the
/// following routines can be used to control heap memory at a bit of a
/// lower level:
///
/// * [`Config::nfa_size_limit`] controls how big _any_ of the NFAs are
/// allowed to be.
/// * [`Config::onepass_size_limit`] controls how big the one-pass DFA is
/// allowed to be.
/// * [`Config::hybrid_cache_capacity`] controls how much memory the lazy
/// DFA is permitted to allocate to store its transition table.
/// * [`Config::dfa_size_limit`] controls how big a fully compiled DFA is
/// allowed to be.
/// * [`Config::dfa_state_limit`] controls the conditions under which the
/// meta regex engine will even attempt to build a fully compiled DFA.
#[inline]
pub fn memory_usage(&self) -> usize {
self.imp.strat.memory_usage()
}
}
impl Clone for Regex {
fn clone(&self) -> Regex {
let imp = Arc::clone(&self.imp);
let pool = {
let strat = Arc::clone(&imp.strat);
let create: CachePoolFn = Box::new(move || strat.create_cache());
Pool::new(create)
};
Regex { imp, pool }
}
}
#[derive(Clone, Debug)]
pub(crate) struct RegexInfo(Arc<RegexInfoI>);
#[derive(Clone, Debug)]
struct RegexInfoI {
config: Config,
props: Vec<hir::Properties>,
props_union: hir::Properties,
}
impl RegexInfo {
fn new(config: Config, hirs: &[&Hir]) -> RegexInfo {
// Collect all of the properties from each of the HIRs, and also
// union them into one big set of properties representing all HIRs
// as if they were in one big alternation.
let mut props = vec![];
for hir in hirs.iter() {
props.push(hir.properties().clone());
}
let props_union = hir::Properties::union(&props);
RegexInfo(Arc::new(RegexInfoI { config, props, props_union }))
}
pub(crate) fn config(&self) -> &Config {
&self.0.config
}
pub(crate) fn props(&self) -> &[hir::Properties] {
&self.0.props
}
pub(crate) fn props_union(&self) -> &hir::Properties {
&self.0.props_union
}
pub(crate) fn pattern_len(&self) -> usize {
self.props().len()
}
pub(crate) fn memory_usage(&self) -> usize {
self.props().iter().map(|p| p.memory_usage()).sum::<usize>()
+ self.props_union().memory_usage()
}
/// Returns true when the search is guaranteed to be anchored. That is,
/// when a match is reported, its offset is guaranteed to correspond to
/// the start of the search.
///
/// This includes returning true when `input` _isn't_ anchored but the
/// underlying regex is.
#[cfg_attr(feature = "perf-inline", inline(always))]
pub(crate) fn is_anchored_start(&self, input: &Input<'_>) -> bool {
input.get_anchored().is_anchored() || self.is_always_anchored_start()
}
/// Returns true when this regex is always anchored to the start of a
/// search. And in particular, that regardless of an `Input` configuration,
/// if any match is reported it must start at `0`.
#[cfg_attr(feature = "perf-inline", inline(always))]
pub(crate) fn is_always_anchored_start(&self) -> bool {
use regex_syntax::hir::Look;
self.props_union().look_set_prefix().contains(Look::Start)
}
/// Returns true when this regex is always anchored to the end of a
/// search. And in particular, that regardless of an `Input` configuration,
/// if any match is reported it must end at the end of the haystack.
#[cfg_attr(feature = "perf-inline", inline(always))]
pub(crate) fn is_always_anchored_end(&self) -> bool {
use regex_syntax::hir::Look;
self.props_union().look_set_suffix().contains(Look::End)
}
/// Returns true if and only if it is known that a match is impossible
/// for the given input. This is useful for short-circuiting and avoiding
/// running the regex engine if it's known no match can be reported.
///
/// Note that this doesn't necessarily detect every possible case. For
/// example, when `pattern_len() == 0`, a match is impossible, but that
/// case is so rare that it's fine to be handled by the regex engine
/// itself. That is, it's not worth the cost of adding it here in order to
/// make it a little faster. The reason is that this is called for every
/// search. so there is some cost to adding checks here. Arguably, some of
/// the checks that are here already probably shouldn't be here...
#[cfg_attr(feature = "perf-inline", inline(always))]
fn is_impossible(&self, input: &Input<'_>) -> bool {
// The underlying regex is anchored, so if we don't start the search
// at position 0, a match is impossible, because the anchor can only
// match at position 0.
if input.start() > 0 && self.is_always_anchored_start() {
return true;
}
// Same idea, but for the end anchor.
if input.end() < input.haystack().len()
&& self.is_always_anchored_end()
{
return true;
}
// If the haystack is smaller than the minimum length required, then
// we know there can be no match.
let minlen = match self.props_union().minimum_len() {
None => return false,
Some(minlen) => minlen,
};
if input.get_span().len() < minlen {
return true;
}
// Same idea as minimum, but for maximum. This is trickier. We can
// only apply the maximum when we know the entire span that we're
// searching *has* to match according to the regex (and possibly the
// input configuration). If we know there is too much for the regex
// to match, we can bail early.
//
// I don't think we can apply the maximum otherwise unfortunately.
if self.is_anchored_start(input) && self.is_always_anchored_end() {
let maxlen = match self.props_union().maximum_len() {
None => return false,
Some(maxlen) => maxlen,
};
if input.get_span().len() > maxlen {
return true;
}
}
false
}
}
/// An iterator over all non-overlapping matches.
///
/// The iterator yields a [`Match`] value until no more matches could be found.
///
/// The lifetime parameters are as follows:
///
/// * `'r` represents the lifetime of the `Regex` that produced this iterator.
/// * `'h` represents the lifetime of the haystack being searched.
///
/// This iterator can be created with the [`Regex::find_iter`] method.
#[derive(Debug)]
pub struct FindMatches<'r, 'h> {
re: &'r Regex,
cache: CachePoolGuard<'r>,
it: iter::Searcher<'h>,
}
impl<'r, 'h> FindMatches<'r, 'h> {
/// Returns the `Regex` value that created this iterator.
#[inline]
pub fn regex(&self) -> &'r Regex {
self.re
}
/// Returns the current `Input` associated with this iterator.
///
/// The `start` position on the given `Input` may change during iteration,
/// but all other values are guaranteed to remain invariant.
#[inline]
pub fn input<'s>(&'s self) -> &'s Input<'h> {
self.it.input()
}
}
impl<'r, 'h> Iterator for FindMatches<'r, 'h> {
type Item = Match;
#[inline]
fn next(&mut self) -> Option<Match> {
let FindMatches { re, ref mut cache, ref mut it } = *self;
it.advance(|input| Ok(re.search_with(cache, input)))
}
#[inline]
fn count(self) -> usize {
// If all we care about is a count of matches, then we only need to
// find the end position of each match. This can give us a 2x perf
// boost in some cases, because it avoids needing to do a reverse scan
// to find the start of a match.
let FindMatches { re, mut cache, it } = self;
// This does the deref for PoolGuard once instead of every iter.
let cache = &mut *cache;
it.into_half_matches_iter(
|input| Ok(re.search_half_with(cache, input)),
)
.count()
}
}
impl<'r, 'h> core::iter::FusedIterator for FindMatches<'r, 'h> {}
/// An iterator over all non-overlapping leftmost matches with their capturing
/// groups.
///
/// The iterator yields a [`Captures`] value until no more matches could be
/// found.
///
/// The lifetime parameters are as follows:
///
/// * `'r` represents the lifetime of the `Regex` that produced this iterator.
/// * `'h` represents the lifetime of the haystack being searched.
///
/// This iterator can be created with the [`Regex::captures_iter`] method.
#[derive(Debug)]
pub struct CapturesMatches<'r, 'h> {
re: &'r Regex,
cache: CachePoolGuard<'r>,
caps: Captures,
it: iter::Searcher<'h>,
}
impl<'r, 'h> CapturesMatches<'r, 'h> {
/// Returns the `Regex` value that created this iterator.
#[inline]
pub fn regex(&self) -> &'r Regex {
self.re
}
/// Returns the current `Input` associated with this iterator.
///
/// The `start` position on the given `Input` may change during iteration,
/// but all other values are guaranteed to remain invariant.
#[inline]
pub fn input<'s>(&'s self) -> &'s Input<'h> {
self.it.input()
}
}
impl<'r, 'h> Iterator for CapturesMatches<'r, 'h> {
type Item = Captures;
#[inline]
fn next(&mut self) -> Option<Captures> {
// Splitting 'self' apart seems necessary to appease borrowck.
let CapturesMatches { re, ref mut cache, ref mut caps, ref mut it } =
*self;
let _ = it.advance(|input| {
re.search_captures_with(cache, input, caps);
Ok(caps.get_match())
});
if caps.is_match() {
Some(caps.clone())
} else {
None
}
}
#[inline]
fn count(self) -> usize {
let CapturesMatches { re, mut cache, it, .. } = self;
// This does the deref for PoolGuard once instead of every iter.
let cache = &mut *cache;
it.into_half_matches_iter(
|input| Ok(re.search_half_with(cache, input)),
)
.count()
}
}
impl<'r, 'h> core::iter::FusedIterator for CapturesMatches<'r, 'h> {}
/// Yields all substrings delimited by a regular expression match.
///
/// The spans correspond to the offsets between matches.
///
/// The lifetime parameters are as follows:
///
/// * `'r` represents the lifetime of the `Regex` that produced this iterator.
/// * `'h` represents the lifetime of the haystack being searched.
///
/// This iterator can be created with the [`Regex::split`] method.
#[derive(Debug)]
pub struct Split<'r, 'h> {
finder: FindMatches<'r, 'h>,
last: usize,
}
impl<'r, 'h> Split<'r, 'h> {
/// Returns the current `Input` associated with this iterator.
///
/// The `start` position on the given `Input` may change during iteration,
/// but all other values are guaranteed to remain invariant.
#[inline]
pub fn input<'s>(&'s self) -> &'s Input<'h> {
self.finder.input()
}
}
impl<'r, 'h> Iterator for Split<'r, 'h> {
type Item = Span;
fn next(&mut self) -> Option<Span> {
match self.finder.next() {
None => {
let len = self.finder.it.input().haystack().len();
if self.last > len {
None
} else {
let span = Span::from(self.last..len);
self.last = len + 1; // Next call will return None
Some(span)
}
}
Some(m) => {
let span = Span::from(self.last..m.start());
self.last = m.end();
Some(span)
}
}
}
}
impl<'r, 'h> core::iter::FusedIterator for Split<'r, 'h> {}
/// Yields at most `N` spans delimited by a regular expression match.
///
/// The spans correspond to the offsets between matches. The last span will be
/// whatever remains after splitting.
///
/// The lifetime parameters are as follows:
///
/// * `'r` represents the lifetime of the `Regex` that produced this iterator.
/// * `'h` represents the lifetime of the haystack being searched.
///
/// This iterator can be created with the [`Regex::splitn`] method.
#[derive(Debug)]
pub struct SplitN<'r, 'h> {
splits: Split<'r, 'h>,
limit: usize,
}
impl<'r, 'h> SplitN<'r, 'h> {
/// Returns the current `Input` associated with this iterator.
///
/// The `start` position on the given `Input` may change during iteration,
/// but all other values are guaranteed to remain invariant.
#[inline]
pub fn input<'s>(&'s self) -> &'s Input<'h> {
self.splits.input()
}
}
impl<'r, 'h> Iterator for SplitN<'r, 'h> {
type Item = Span;
fn next(&mut self) -> Option<Span> {
if self.limit == 0 {
return None;
}
self.limit -= 1;
if self.limit > 0 {
return self.splits.next();
}
let len = self.splits.finder.it.input().haystack().len();
if self.splits.last > len {
// We've already returned all substrings.
None
} else {
// self.n == 0, so future calls will return None immediately
Some(Span::from(self.splits.last..len))
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
(0, Some(self.limit))
}
}
impl<'r, 'h> core::iter::FusedIterator for SplitN<'r, 'h> {}
/// Represents mutable scratch space used by regex engines during a search.
///
/// Most of the regex engines in this crate require some kind of
/// mutable state in order to execute a search. This mutable state is
/// explicitly separated from the core regex object (such as a
/// [`thompson::NFA`](crate::nfa::thompson::NFA)) so that the read-only regex
/// object can be shared across multiple threads simultaneously without any
/// synchronization. Conversely, a `Cache` must either be duplicated if using
/// the same `Regex` from multiple threads, or else there must be some kind of
/// synchronization that guarantees exclusive access while it's in use by one
/// thread.
///
/// A `Regex` attempts to do this synchronization for you by using a thread
/// pool internally. Its size scales roughly with the number of simultaneous
/// regex searches.
///
/// For cases where one does not want to rely on a `Regex`'s internal thread
/// pool, lower level routines such as [`Regex::search_with`] are provided
/// that permit callers to pass a `Cache` into the search routine explicitly.
///
/// General advice is that the thread pool is often more than good enough.
/// However, it may be possible to observe the effects of its latency,
/// especially when searching many small haystacks from many threads
/// simultaneously.
///
/// Caches can be created from their corresponding `Regex` via
/// [`Regex::create_cache`]. A cache can only be used with either the `Regex`
/// that created it, or the `Regex` that was most recently used to reset it
/// with [`Cache::reset`]. Using a cache with any other `Regex` may result in
/// panics or incorrect results.
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Input, Match};
///
/// let re = Regex::new(r"(?-u)m\w+\s+m\w+")?;
/// let mut cache = re.create_cache();
/// let input = Input::new("crazy janey and her mission man");
/// assert_eq!(
/// Some(Match::must(0, 20..31)),
/// re.search_with(&mut cache, &input),
/// );
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[derive(Debug, Clone)]
pub struct Cache {
pub(crate) capmatches: Captures,
pub(crate) pikevm: wrappers::PikeVMCache,
pub(crate) backtrack: wrappers::BoundedBacktrackerCache,
pub(crate) onepass: wrappers::OnePassCache,
pub(crate) hybrid: wrappers::HybridCache,
pub(crate) revhybrid: wrappers::ReverseHybridCache,
}
impl Cache {
/// Creates a new `Cache` for use with this regex.
///
/// The cache returned should only be used for searches for the given
/// `Regex`. If you want to reuse the cache for another `Regex`, then you
/// must call [`Cache::reset`] with that `Regex`.
pub fn new(re: &Regex) -> Cache {
re.create_cache()
}
/// Reset this cache such that it can be used for searching with the given
/// `Regex` (and only that `Regex`).
///
/// A cache reset permits potentially reusing memory already allocated in
/// this cache with a different `Regex`.
///
/// # Example
///
/// This shows how to re-purpose a cache for use with a different `Regex`.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{meta::Regex, Match, Input};
///
/// let re1 = Regex::new(r"\w")?;
/// let re2 = Regex::new(r"\W")?;
///
/// let mut cache = re1.create_cache();
/// assert_eq!(
/// Some(Match::must(0, 0..2)),
/// re1.search_with(&mut cache, &Input::new("Δ")),
/// );
///
/// // Using 'cache' with re2 is not allowed. It may result in panics or
/// // incorrect results. In order to re-purpose the cache, we must reset
/// // it with the Regex we'd like to use it with.
/// //
/// // Similarly, after this reset, using the cache with 're1' is also not
/// // allowed.
/// cache.reset(&re2);
/// assert_eq!(
/// Some(Match::must(0, 0..3)),
/// re2.search_with(&mut cache, &Input::new("☃")),
/// );
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn reset(&mut self, re: &Regex) {
re.imp.strat.reset_cache(self)
}
/// Returns the heap memory usage, in bytes, of this cache.
///
/// This does **not** include the stack size used up by this cache. To
/// compute that, use `std::mem::size_of::<Cache>()`.
pub fn memory_usage(&self) -> usize {
let mut bytes = 0;
bytes += self.pikevm.memory_usage();
bytes += self.backtrack.memory_usage();
bytes += self.onepass.memory_usage();
bytes += self.hybrid.memory_usage();
bytes += self.revhybrid.memory_usage();
bytes
}
}
/// An object describing the configuration of a `Regex`.
///
/// This configuration only includes options for the
/// non-syntax behavior of a `Regex`, and can be applied via the
/// [`Builder::configure`] method. For configuring the syntax options, see
/// [`util::syntax::Config`](crate::util::syntax::Config).
///
/// # Example: lower the NFA size limit
///
/// In some cases, the default size limit might be too big. The size limit can
/// be lowered, which will prevent large regex patterns from compiling.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::meta::Regex;
///
/// let result = Regex::builder()
/// .configure(Regex::config().nfa_size_limit(Some(20 * (1<<10))))
/// // Not even 20KB is enough to build a single large Unicode class!
/// .build(r"\pL");
/// assert!(result.is_err());
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[derive(Clone, Debug, Default)]
pub struct Config {
// As with other configuration types in this crate, we put all our knobs
// in options so that we can distinguish between "default" and "not set."
// This makes it possible to easily combine multiple configurations
// without default values overwriting explicitly specified values. See the
// 'overwrite' method.
//
// For docs on the fields below, see the corresponding method setters.
match_kind: Option<MatchKind>,
utf8_empty: Option<bool>,
autopre: Option<bool>,
pre: Option<Option<Prefilter>>,
which_captures: Option<WhichCaptures>,
nfa_size_limit: Option<Option<usize>>,
onepass_size_limit: Option<Option<usize>>,
hybrid_cache_capacity: Option<usize>,
hybrid: Option<bool>,
dfa: Option<bool>,
dfa_size_limit: Option<Option<usize>>,
dfa_state_limit: Option<Option<usize>>,
onepass: Option<bool>,
backtrack: Option<bool>,
byte_classes: Option<bool>,
line_terminator: Option<u8>,
}
impl Config {
/// Create a new configuration object for a `Regex`.
pub fn new() -> Config {
Config::default()
}
/// Set the match semantics for a `Regex`.
///
/// The default value is [`MatchKind::LeftmostFirst`].
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Match, MatchKind};
///
/// // By default, leftmost-first semantics are used, which
/// // disambiguates matches at the same position by selecting
/// // the one that corresponds earlier in the pattern.
/// let re = Regex::new("sam|samwise")?;
/// assert_eq!(Some(Match::must(0, 0..3)), re.find("samwise"));
///
/// // But with 'all' semantics, match priority is ignored
/// // and all match states are included. When coupled with
/// // a leftmost search, the search will report the last
/// // possible match.
/// let re = Regex::builder()
/// .configure(Regex::config().match_kind(MatchKind::All))
/// .build("sam|samwise")?;
/// assert_eq!(Some(Match::must(0, 0..7)), re.find("samwise"));
/// // Beware that this can lead to skipping matches!
/// // Usually 'all' is used for anchored reverse searches
/// // only, or for overlapping searches.
/// assert_eq!(Some(Match::must(0, 4..11)), re.find("sam samwise"));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn match_kind(self, kind: MatchKind) -> Config {
Config { match_kind: Some(kind), ..self }
}
/// Toggles whether empty matches are permitted to occur between the code
/// units of a UTF-8 encoded codepoint.
///
/// This should generally be enabled when search a `&str` or anything that
/// you otherwise know is valid UTF-8. It should be disabled in all other
/// cases. Namely, if the haystack is not valid UTF-8 and this is enabled,
/// then behavior is unspecified.
///
/// By default, this is enabled.
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Match};
///
/// let re = Regex::new("")?;
/// let got: Vec<Match> = re.find_iter("☃").collect();
/// // Matches only occur at the beginning and end of the snowman.
/// assert_eq!(got, vec![
/// Match::must(0, 0..0),
/// Match::must(0, 3..3),
/// ]);
///
/// let re = Regex::builder()
/// .configure(Regex::config().utf8_empty(false))
/// .build("")?;
/// let got: Vec<Match> = re.find_iter("☃").collect();
/// // Matches now occur at every position!
/// assert_eq!(got, vec![
/// Match::must(0, 0..0),
/// Match::must(0, 1..1),
/// Match::must(0, 2..2),
/// Match::must(0, 3..3),
/// ]);
///
/// Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn utf8_empty(self, yes: bool) -> Config {
Config { utf8_empty: Some(yes), ..self }
}
/// Toggles whether automatic prefilter support is enabled.
///
/// If this is disabled and [`Config::prefilter`] is not set, then the
/// meta regex engine will not use any prefilters. This can sometimes
/// be beneficial in cases where you know (or have measured) that the
/// prefilter leads to overall worse search performance.
///
/// By default, this is enabled.
///
/// # Example
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{meta::Regex, Match};
///
/// let re = Regex::builder()
/// .configure(Regex::config().auto_prefilter(false))
/// .build(r"Bruce \w+")?;
/// let hay = "Hello Bruce Springsteen!";
/// assert_eq!(Some(Match::must(0, 6..23)), re.find(hay));
///
/// Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn auto_prefilter(self, yes: bool) -> Config {
Config { autopre: Some(yes), ..self }
}
/// Overrides and sets the prefilter to use inside a `Regex`.
///
/// This permits one to forcefully set a prefilter in cases where the
/// caller knows better than whatever the automatic prefilter logic is
/// capable of.
///
/// By default, this is set to `None` and an automatic prefilter will be
/// used if one could be built. (Assuming [`Config::auto_prefilter`] is
/// enabled, which it is by default.)
///
/// # Example
///
/// This example shows how to set your own prefilter. In the case of a
/// pattern like `Bruce \w+`, the automatic prefilter is likely to be
/// constructed in a way that it will look for occurrences of `Bruce `.
/// In most cases, this is the best choice. But in some cases, it may be
/// the case that running `memchr` on `B` is the best choice. One can
/// achieve that behavior by overriding the automatic prefilter logic
/// and providing a prefilter that just matches `B`.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{
/// meta::Regex,
/// util::prefilter::Prefilter,
/// Match, MatchKind,
/// };
///
/// let pre = Prefilter::new(MatchKind::LeftmostFirst, &["B"])
/// .expect("a prefilter");
/// let re = Regex::builder()
/// .configure(Regex::config().prefilter(Some(pre)))
/// .build(r"Bruce \w+")?;
/// let hay = "Hello Bruce Springsteen!";
/// assert_eq!(Some(Match::must(0, 6..23)), re.find(hay));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: incorrect prefilters can lead to incorrect results!
///
/// Be warned that setting an incorrect prefilter can lead to missed
/// matches. So if you use this option, ensure your prefilter can _never_
/// report false negatives. (A false positive is, on the other hand, quite
/// okay and generally unavoidable.)
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::{
/// meta::Regex,
/// util::prefilter::Prefilter,
/// Match, MatchKind,
/// };
///
/// let pre = Prefilter::new(MatchKind::LeftmostFirst, &["Z"])
/// .expect("a prefilter");
/// let re = Regex::builder()
/// .configure(Regex::config().prefilter(Some(pre)))
/// .build(r"Bruce \w+")?;
/// let hay = "Hello Bruce Springsteen!";
/// // Oops! No match found, but there should be one!
/// assert_eq!(None, re.find(hay));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn prefilter(self, pre: Option<Prefilter>) -> Config {
Config { pre: Some(pre), ..self }
}
/// Configures what kinds of groups are compiled as "capturing" in the
/// underlying regex engine.
///
/// This is set to [`WhichCaptures::All`] by default. Callers may wish to
/// use [`WhichCaptures::Implicit`] in cases where one wants avoid the
/// overhead of capture states for explicit groups.
///
/// Note that another approach to avoiding the overhead of capture groups
/// is by using non-capturing groups in the regex pattern. That is,
/// `(?:a)` instead of `(a)`. This option is useful when you can't control
/// the concrete syntax but know that you don't need the underlying capture
/// states. For example, using `WhichCaptures::Implicit` will behave as if
/// all explicit capturing groups in the pattern were non-capturing.
///
/// Setting this to `WhichCaptures::None` is usually not the right thing to
/// do. When no capture states are compiled, some regex engines (such as
/// the `PikeVM`) won't be able to report match offsets. This will manifest
/// as no match being found.
///
/// # Example
///
/// This example demonstrates how the results of capture groups can change
/// based on this option. First we show the default (all capture groups in
/// the pattern are capturing):
///
/// ```
/// use regex_automata::{meta::Regex, Match, Span};
///
/// let re = Regex::new(r"foo([0-9]+)bar")?;
/// let hay = "foo123bar";
///
/// let mut caps = re.create_captures();
/// re.captures(hay, &mut caps);
/// assert_eq!(Some(Span::from(0..9)), caps.get_group(0));
/// assert_eq!(Some(Span::from(3..6)), caps.get_group(1));
///
/// Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// And now we show the behavior when we only include implicit capture
/// groups. In this case, we can only find the overall match span, but the
/// spans of any other explicit group don't exist because they are treated
/// as non-capturing. (In effect, when `WhichCaptures::Implicit` is used,
/// there is no real point in using [`Regex::captures`] since it will never
/// be able to report more information than [`Regex::find`].)
///
/// ```
/// use regex_automata::{
/// meta::Regex,
/// nfa::thompson::WhichCaptures,
/// Match,
/// Span,
/// };
///
/// let re = Regex::builder()
/// .configure(Regex::config().which_captures(WhichCaptures::Implicit))
/// .build(r"foo([0-9]+)bar")?;
/// let hay = "foo123bar";
///
/// let mut caps = re.create_captures();
/// re.captures(hay, &mut caps);
/// assert_eq!(Some(Span::from(0..9)), caps.get_group(0));
/// assert_eq!(None, caps.get_group(1));
///
/// Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn which_captures(mut self, which_captures: WhichCaptures) -> Config {
self.which_captures = Some(which_captures);
self
}
/// Sets the size limit, in bytes, to enforce on the construction of every
/// NFA build by the meta regex engine.
///
/// Setting it to `None` disables the limit. This is not recommended if
/// you're compiling untrusted patterns.
///
/// Note that this limit is applied to _each_ NFA built, and if any of
/// them exceed the limit, then construction will fail. This limit does
/// _not_ correspond to the total memory used by all NFAs in the meta regex
/// engine.
///
/// This defaults to some reasonable number that permits most reasonable
/// patterns.
///
/// # Example
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::meta::Regex;
///
/// let result = Regex::builder()
/// .configure(Regex::config().nfa_size_limit(Some(20 * (1<<10))))
/// // Not even 20KB is enough to build a single large Unicode class!
/// .build(r"\pL");
/// assert!(result.is_err());
///
/// // But notice that building such a regex with the exact same limit
/// // can succeed depending on other aspects of the configuration. For
/// // example, a single *forward* NFA will (at time of writing) fit into
/// // the 20KB limit, but a *reverse* NFA of the same pattern will not.
/// // So if one configures a meta regex such that a reverse NFA is never
/// // needed and thus never built, then the 20KB limit will be enough for
/// // a pattern like \pL!
/// let result = Regex::builder()
/// .configure(Regex::config()
/// .nfa_size_limit(Some(20 * (1<<10)))
/// // The DFAs are the only thing that (currently) need a reverse
/// // NFA. So if both are disabled, the meta regex engine will
/// // skip building the reverse NFA. Note that this isn't an API
/// // guarantee. A future semver compatible version may introduce
/// // new use cases for a reverse NFA.
/// .hybrid(false)
/// .dfa(false)
/// )
/// // Not even 20KB is enough to build a single large Unicode class!
/// .build(r"\pL");
/// assert!(result.is_ok());
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn nfa_size_limit(self, limit: Option<usize>) -> Config {
Config { nfa_size_limit: Some(limit), ..self }
}
/// Sets the size limit, in bytes, for the one-pass DFA.
///
/// Setting it to `None` disables the limit. Disabling the limit is
/// strongly discouraged when compiling untrusted patterns. Even if the
/// patterns are trusted, it still may not be a good idea, since a one-pass
/// DFA can use a lot of memory. With that said, as the size of a regex
/// increases, the likelihood of it being one-pass likely decreases.
///
/// This defaults to some reasonable number that permits most reasonable
/// one-pass patterns.
///
/// # Example
///
/// This shows how to set the one-pass DFA size limit. Note that since
/// a one-pass DFA is an optional component of the meta regex engine,
/// this size limit only impacts what is built internally and will never
/// determine whether a `Regex` itself fails to build.
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::meta::Regex;
///
/// let result = Regex::builder()
/// .configure(Regex::config().onepass_size_limit(Some(2 * (1<<20))))
/// .build(r"\pL{5}");
/// assert!(result.is_ok());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn onepass_size_limit(self, limit: Option<usize>) -> Config {
Config { onepass_size_limit: Some(limit), ..self }
}
/// Set the cache capacity, in bytes, for the lazy DFA.
///
/// The cache capacity of the lazy DFA determines approximately how much
/// heap memory it is allowed to use to store its state transitions. The
/// state transitions are computed at search time, and if the cache fills
/// up it, it is cleared. At this point, any previously generated state
/// transitions are lost and are re-generated if they're needed again.
///
/// This sort of cache filling and clearing works quite well _so long as
/// cache clearing happens infrequently_. If it happens too often, then the
/// meta regex engine will stop using the lazy DFA and switch over to a
/// different regex engine.
///
/// In cases where the cache is cleared too often, it may be possible to
/// give the cache more space and reduce (or eliminate) how often it is
/// cleared. Similarly, sometimes a regex is so big that the lazy DFA isn't
/// used at all if its cache capacity isn't big enough.
///
/// The capacity set here is a _limit_ on how much memory is used. The
/// actual memory used is only allocated as it's needed.
///
/// Determining the right value for this is a little tricky and will likely
/// required some profiling. Enabling the `logging` feature and setting the
/// log level to `trace` will also tell you how often the cache is being
/// cleared.
///
/// # Example
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::meta::Regex;
///
/// let result = Regex::builder()
/// .configure(Regex::config().hybrid_cache_capacity(20 * (1<<20)))
/// .build(r"\pL{5}");
/// assert!(result.is_ok());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn hybrid_cache_capacity(self, limit: usize) -> Config {
Config { hybrid_cache_capacity: Some(limit), ..self }
}
/// Sets the size limit, in bytes, for heap memory used for a fully
/// compiled DFA.
///
/// **NOTE:** If you increase this, you'll likely also need to increase
/// [`Config::dfa_state_limit`].
///
/// In contrast to the lazy DFA, building a full DFA requires computing
/// all of its state transitions up front. This can be a very expensive
/// process, and runs in worst case `2^n` time and space (where `n` is
/// proportional to the size of the regex). However, a full DFA unlocks
/// some additional optimization opportunities.
///
/// Because full DFAs can be so expensive, the default limits for them are
/// incredibly small. Generally speaking, if your regex is moderately big
/// or if you're using Unicode features (`\w` is Unicode-aware by default
/// for example), then you can expect that the meta regex engine won't even
/// attempt to build a DFA for it.
///
/// If this and [`Config::dfa_state_limit`] are set to `None`, then the
/// meta regex will not use any sort of limits when deciding whether to
/// build a DFA. This in turn makes construction of a `Regex` take
/// worst case exponential time and space. Even short patterns can result
/// in huge space blow ups. So it is strongly recommended to keep some kind
/// of limit set!
///
/// The default is set to a small number that permits some simple regexes
/// to get compiled into DFAs in reasonable time.
///
/// # Example
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::meta::Regex;
///
/// let result = Regex::builder()
/// // 100MB is much bigger than the default.
/// .configure(Regex::config()
/// .dfa_size_limit(Some(100 * (1<<20)))
/// // We don't care about size too much here, so just
/// // remove the NFA state limit altogether.
/// .dfa_state_limit(None))
/// .build(r"\pL{5}");
/// assert!(result.is_ok());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn dfa_size_limit(self, limit: Option<usize>) -> Config {
Config { dfa_size_limit: Some(limit), ..self }
}
/// Sets a limit on the total number of NFA states, beyond which, a full
/// DFA is not attempted to be compiled.
///
/// This limit works in concert with [`Config::dfa_size_limit`]. Namely,
/// where as `Config::dfa_size_limit` is applied by attempting to construct
/// a DFA, this limit is used to avoid the attempt in the first place. This
/// is useful to avoid hefty initialization costs associated with building
/// a DFA for cases where it is obvious the DFA will ultimately be too big.
///
/// By default, this is set to a very small number.
///
/// # Example
///
/// ```
/// # if cfg!(miri) { return Ok(()); } // miri takes too long
/// use regex_automata::meta::Regex;
///
/// let result = Regex::builder()
/// .configure(Regex::config()
/// // Sometimes the default state limit rejects DFAs even
/// // if they would fit in the size limit. Here, we disable
/// // the check on the number of NFA states and just rely on
/// // the size limit.
/// .dfa_state_limit(None))
/// .build(r"(?-u)\w{30}");
/// assert!(result.is_ok());
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn dfa_state_limit(self, limit: Option<usize>) -> Config {
Config { dfa_state_limit: Some(limit), ..self }
}
/// Whether to attempt to shrink the size of the alphabet for the regex
/// pattern or not. When enabled, the alphabet is shrunk into a set of
/// equivalence classes, where every byte in the same equivalence class
/// cannot discriminate between a match or non-match.
///
/// **WARNING:** This is only useful for debugging DFAs. Disabling this
/// does not yield any speed advantages. Indeed, disabling it can result
/// in much higher memory usage. Disabling byte classes is useful for
/// debugging the actual generated transitions because it lets one see the
/// transitions defined on actual bytes instead of the equivalence classes.
///
/// This option is enabled by default and should never be disabled unless
/// one is debugging the meta regex engine's internals.
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, Match};
///
/// let re = Regex::builder()
/// .configure(Regex::config().byte_classes(false))
/// .build(r"[a-z]+")?;
/// let hay = "!!quux!!";
/// assert_eq!(Some(Match::must(0, 2..6)), re.find(hay));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn byte_classes(self, yes: bool) -> Config {
Config { byte_classes: Some(yes), ..self }
}
/// Set the line terminator to be used by the `^` and `$` anchors in
/// multi-line mode.
///
/// This option has no effect when CRLF mode is enabled. That is,
/// regardless of this setting, `(?Rm:^)` and `(?Rm:$)` will always treat
/// `\r` and `\n` as line terminators (and will never match between a `\r`
/// and a `\n`).
///
/// By default, `\n` is the line terminator.
///
/// **Warning**: This does not change the behavior of `.`. To do that,
/// you'll need to configure the syntax option
/// [`syntax::Config::line_terminator`](crate::util::syntax::Config::line_terminator)
/// in addition to this. Otherwise, `.` will continue to match any
/// character other than `\n`.
///
/// # Example
///
/// ```
/// use regex_automata::{meta::Regex, util::syntax, Match};
///
/// let re = Regex::builder()
/// .syntax(syntax::Config::new().multi_line(true))
/// .configure(Regex::config().line_terminator(b'\x00'))
/// .build(r"^foo$")?;
/// let hay = "\x00foo\x00";
/// assert_eq!(Some(Match::must(0, 1..4)), re.find(hay));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn line_terminator(self, byte: u8) -> Config {
Config { line_terminator: Some(byte), ..self }
}
/// Toggle whether the hybrid NFA/DFA (also known as the "lazy DFA") should
/// be available for use by the meta regex engine.
///
/// Enabling this does not necessarily mean that the lazy DFA will
/// definitely be used. It just means that it will be _available_ for use
/// if the meta regex engine thinks it will be useful.
///
/// When the `hybrid` crate feature is enabled, then this is enabled by
/// default. Otherwise, if the crate feature is disabled, then this is
/// always disabled, regardless of its setting by the caller.
pub fn hybrid(self, yes: bool) -> Config {
Config { hybrid: Some(yes), ..self }
}
/// Toggle whether a fully compiled DFA should be available for use by the
/// meta regex engine.
///
/// Enabling this does not necessarily mean that a DFA will definitely be
/// used. It just means that it will be _available_ for use if the meta
/// regex engine thinks it will be useful.
///
/// When the `dfa-build` crate feature is enabled, then this is enabled by
/// default. Otherwise, if the crate feature is disabled, then this is
/// always disabled, regardless of its setting by the caller.
pub fn dfa(self, yes: bool) -> Config {
Config { dfa: Some(yes), ..self }
}
/// Toggle whether a one-pass DFA should be available for use by the meta
/// regex engine.
///
/// Enabling this does not necessarily mean that a one-pass DFA will
/// definitely be used. It just means that it will be _available_ for
/// use if the meta regex engine thinks it will be useful. (Indeed, a
/// one-pass DFA can only be used when the regex is one-pass. See the
/// [`dfa::onepass`](crate::dfa::onepass) module for more details.)
///
/// When the `dfa-onepass` crate feature is enabled, then this is enabled
/// by default. Otherwise, if the crate feature is disabled, then this is
/// always disabled, regardless of its setting by the caller.
pub fn onepass(self, yes: bool) -> Config {
Config { onepass: Some(yes), ..self }
}
/// Toggle whether a bounded backtracking regex engine should be available
/// for use by the meta regex engine.
///
/// Enabling this does not necessarily mean that a bounded backtracker will
/// definitely be used. It just means that it will be _available_ for use
/// if the meta regex engine thinks it will be useful.
///
/// When the `nfa-backtrack` crate feature is enabled, then this is enabled
/// by default. Otherwise, if the crate feature is disabled, then this is
/// always disabled, regardless of its setting by the caller.
pub fn backtrack(self, yes: bool) -> Config {
Config { backtrack: Some(yes), ..self }
}
/// Returns the match kind on this configuration, as set by
/// [`Config::match_kind`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_match_kind(&self) -> MatchKind {
self.match_kind.unwrap_or(MatchKind::LeftmostFirst)
}
/// Returns whether empty matches must fall on valid UTF-8 boundaries, as
/// set by [`Config::utf8_empty`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_utf8_empty(&self) -> bool {
self.utf8_empty.unwrap_or(true)
}
/// Returns whether automatic prefilters are enabled, as set by
/// [`Config::auto_prefilter`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_auto_prefilter(&self) -> bool {
self.autopre.unwrap_or(true)
}
/// Returns a manually set prefilter, if one was set by
/// [`Config::prefilter`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_prefilter(&self) -> Option<&Prefilter> {
self.pre.as_ref().unwrap_or(&None).as_ref()
}
/// Returns the capture configuration, as set by
/// [`Config::which_captures`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_which_captures(&self) -> WhichCaptures {
self.which_captures.unwrap_or(WhichCaptures::All)
}
/// Returns NFA size limit, as set by [`Config::nfa_size_limit`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_nfa_size_limit(&self) -> Option<usize> {
self.nfa_size_limit.unwrap_or(Some(10 * (1 << 20)))
}
/// Returns one-pass DFA size limit, as set by
/// [`Config::onepass_size_limit`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_onepass_size_limit(&self) -> Option<usize> {
self.onepass_size_limit.unwrap_or(Some(1 * (1 << 20)))
}
/// Returns hybrid NFA/DFA cache capacity, as set by
/// [`Config::hybrid_cache_capacity`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_hybrid_cache_capacity(&self) -> usize {
self.hybrid_cache_capacity.unwrap_or(2 * (1 << 20))
}
/// Returns DFA size limit, as set by [`Config::dfa_size_limit`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_dfa_size_limit(&self) -> Option<usize> {
// The default for this is VERY small because building a full DFA is
// ridiculously costly. But for regexes that are very small, it can be
// beneficial to use a full DFA. In particular, a full DFA can enable
// additional optimizations via something called "accelerated" states.
// Namely, when there's a state with only a few outgoing transitions,
// we can temporary suspend walking the transition table and use memchr
// for just those outgoing transitions to skip ahead very quickly.
//
// Generally speaking, if Unicode is enabled in your regex and you're
// using some kind of Unicode feature, then it's going to blow this
// size limit. Moreover, Unicode tends to defeat the "accelerated"
// state optimization too, so it's a double whammy.
//
// We also use a limit on the number of NFA states to avoid even
// starting the DFA construction process. Namely, DFA construction
// itself could make lots of initial allocs proportional to the size
// of the NFA, and if the NFA is large, it doesn't make sense to pay
// that cost if we know it's likely to be blown by a large margin.
self.dfa_size_limit.unwrap_or(Some(40 * (1 << 10)))
}
/// Returns DFA size limit in terms of the number of states in the NFA, as
/// set by [`Config::dfa_state_limit`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_dfa_state_limit(&self) -> Option<usize> {
// Again, as with the size limit, we keep this very small.
self.dfa_state_limit.unwrap_or(Some(30))
}
/// Returns whether byte classes are enabled, as set by
/// [`Config::byte_classes`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_byte_classes(&self) -> bool {
self.byte_classes.unwrap_or(true)
}
/// Returns the line terminator for this configuration, as set by
/// [`Config::line_terminator`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_line_terminator(&self) -> u8 {
self.line_terminator.unwrap_or(b'\n')
}
/// Returns whether the hybrid NFA/DFA regex engine may be used, as set by
/// [`Config::hybrid`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_hybrid(&self) -> bool {
#[cfg(feature = "hybrid")]
{
self.hybrid.unwrap_or(true)
}
#[cfg(not(feature = "hybrid"))]
{
false
}
}
/// Returns whether the DFA regex engine may be used, as set by
/// [`Config::dfa`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_dfa(&self) -> bool {
#[cfg(feature = "dfa-build")]
{
self.dfa.unwrap_or(true)
}
#[cfg(not(feature = "dfa-build"))]
{
false
}
}
/// Returns whether the one-pass DFA regex engine may be used, as set by
/// [`Config::onepass`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_onepass(&self) -> bool {
#[cfg(feature = "dfa-onepass")]
{
self.onepass.unwrap_or(true)
}
#[cfg(not(feature = "dfa-onepass"))]
{
false
}
}
/// Returns whether the bounded backtracking regex engine may be used, as
/// set by [`Config::backtrack`].
///
/// If it was not explicitly set, then a default value is returned.
pub fn get_backtrack(&self) -> bool {
#[cfg(feature = "nfa-backtrack")]
{
self.backtrack.unwrap_or(true)
}
#[cfg(not(feature = "nfa-backtrack"))]
{
false
}
}
/// Overwrite the default configuration such that the options in `o` are
/// always used. If an option in `o` is not set, then the corresponding
/// option in `self` is used. If it's not set in `self` either, then it
/// remains not set.
pub(crate) fn overwrite(&self, o: Config) -> Config {
Config {
match_kind: o.match_kind.or(self.match_kind),
utf8_empty: o.utf8_empty.or(self.utf8_empty),
autopre: o.autopre.or(self.autopre),
pre: o.pre.or_else(|| self.pre.clone()),
which_captures: o.which_captures.or(self.which_captures),
nfa_size_limit: o.nfa_size_limit.or(self.nfa_size_limit),
onepass_size_limit: o
.onepass_size_limit
.or(self.onepass_size_limit),
hybrid_cache_capacity: o
.hybrid_cache_capacity
.or(self.hybrid_cache_capacity),
hybrid: o.hybrid.or(self.hybrid),
dfa: o.dfa.or(self.dfa),
dfa_size_limit: o.dfa_size_limit.or(self.dfa_size_limit),
dfa_state_limit: o.dfa_state_limit.or(self.dfa_state_limit),
onepass: o.onepass.or(self.onepass),
backtrack: o.backtrack.or(self.backtrack),
byte_classes: o.byte_classes.or(self.byte_classes),
line_terminator: o.line_terminator.or(self.line_terminator),
}
}
}
/// A builder for configuring and constructing a `Regex`.
///
/// The builder permits configuring two different aspects of a `Regex`:
///
/// * [`Builder::configure`] will set high-level configuration options as
/// described by a [`Config`].
/// * [`Builder::syntax`] will set the syntax level configuration options
/// as described by a [`util::syntax::Config`](crate::util::syntax::Config).
/// This only applies when building a `Regex` from pattern strings.
///
/// Once configured, the builder can then be used to construct a `Regex` from
/// one of 4 different inputs:
///
/// * [`Builder::build`] creates a regex from a single pattern string.
/// * [`Builder::build_many`] creates a regex from many pattern strings.
/// * [`Builder::build_from_hir`] creates a regex from a
/// [`regex-syntax::Hir`](Hir) expression.
/// * [`Builder::build_many_from_hir`] creates a regex from many
/// [`regex-syntax::Hir`](Hir) expressions.
///
/// The latter two methods in particular provide a way to construct a fully
/// feature regular expression matcher directly from an `Hir` expression
/// without having to first convert it to a string. (This is in contrast to the
/// top-level `regex` crate which intentionally provides no such API in order
/// to avoid making `regex-syntax` a public dependency.)
///
/// As a convenience, this builder may be created via [`Regex::builder`], which
/// may help avoid an extra import.
///
/// # Example: change the line terminator
///
/// This example shows how to enable multi-line mode by default and change the
/// line terminator to the NUL byte:
///
/// ```
/// use regex_automata::{meta::Regex, util::syntax, Match};
///
/// let re = Regex::builder()
/// .syntax(syntax::Config::new().multi_line(true))
/// .configure(Regex::config().line_terminator(b'\x00'))
/// .build(r"^foo$")?;
/// let hay = "\x00foo\x00";
/// assert_eq!(Some(Match::must(0, 1..4)), re.find(hay));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: disable UTF-8 requirement
///
/// By default, regex patterns are required to match UTF-8. This includes
/// regex patterns that can produce matches of length zero. In the case of an
/// empty match, by default, matches will not appear between the code units of
/// a UTF-8 encoded codepoint.
///
/// However, it can be useful to disable this requirement, particularly if
/// you're searching things like `&[u8]` that are not known to be valid UTF-8.
///
/// ```
/// use regex_automata::{meta::Regex, util::syntax, Match};
///
/// let mut builder = Regex::builder();
/// // Disables the requirement that non-empty matches match UTF-8.
/// builder.syntax(syntax::Config::new().utf8(false));
/// // Disables the requirement that empty matches match UTF-8 boundaries.
/// builder.configure(Regex::config().utf8_empty(false));
///
/// // We can match raw bytes via \xZZ syntax, but we need to disable
/// // Unicode mode to do that. We could disable it everywhere, or just
/// // selectively, as shown here.
/// let re = builder.build(r"(?-u:\xFF)foo(?-u:\xFF)")?;
/// let hay = b"\xFFfoo\xFF";
/// assert_eq!(Some(Match::must(0, 0..5)), re.find(hay));
///
/// // We can also match between code units.
/// let re = builder.build(r"")?;
/// let hay = "☃";
/// assert_eq!(re.find_iter(hay).collect::<Vec<Match>>(), vec![
/// Match::must(0, 0..0),
/// Match::must(0, 1..1),
/// Match::must(0, 2..2),
/// Match::must(0, 3..3),
/// ]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[derive(Clone, Debug)]
pub struct Builder {
config: Config,
ast: ast::parse::ParserBuilder,
hir: hir::translate::TranslatorBuilder,
}
impl Builder {
/// Creates a new builder for configuring and constructing a [`Regex`].
pub fn new() -> Builder {
Builder {
config: Config::default(),
ast: ast::parse::ParserBuilder::new(),
hir: hir::translate::TranslatorBuilder::new(),
}
}
/// Builds a `Regex` from a single pattern string.
///
/// If there was a problem parsing the pattern or a problem turning it into
/// a regex matcher, then an error is returned.
///
/// # Example
///
/// This example shows how to configure syntax options.
///
/// ```
/// use regex_automata::{meta::Regex, util::syntax, Match};
///
/// let re = Regex::builder()
/// .syntax(syntax::Config::new().crlf(true).multi_line(true))
/// .build(r"^foo$")?;
/// let hay = "\r\nfoo\r\n";
/// assert_eq!(Some(Match::must(0, 2..5)), re.find(hay));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn build(&self, pattern: &str) -> Result<Regex, BuildError> {
self.build_many(&[pattern])
}
/// Builds a `Regex` from many pattern strings.
///
/// If there was a problem parsing any of the patterns or a problem turning
/// them into a regex matcher, then an error is returned.
///
/// # Example: finding the pattern that caused an error
///
/// When a syntax error occurs, it is possible to ask which pattern
/// caused the syntax error.
///
/// ```
/// use regex_automata::{meta::Regex, PatternID};
///
/// let err = Regex::builder()
/// .build_many(&["a", "b", r"\p{Foo}", "c"])
/// .unwrap_err();
/// assert_eq!(Some(PatternID::must(2)), err.pattern());
/// ```
///
/// # Example: zero patterns is valid
///
/// Building a regex with zero patterns results in a regex that never
/// matches anything. Because this routine is generic, passing an empty
/// slice usually requires a turbo-fish (or something else to help type
/// inference).
///
/// ```
/// use regex_automata::{meta::Regex, util::syntax, Match};
///
/// let re = Regex::builder()
/// .build_many::<&str>(&[])?;
/// assert_eq!(None, re.find(""));
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn build_many<P: AsRef<str>>(
&self,
patterns: &[P],
) -> Result<Regex, BuildError> {
use crate::util::primitives::IteratorIndexExt;
log! {
debug!("building meta regex with {} patterns:", patterns.len());
for (pid, p) in patterns.iter().with_pattern_ids() {
let p = p.as_ref();
// We might split a grapheme with this truncation logic, but
// that's fine. We at least avoid splitting a codepoint.
let maxoff = p
.char_indices()
.map(|(i, ch)| i + ch.len_utf8())
.take(1000)
.last()
.unwrap_or(0);
if maxoff < p.len() {
debug!("{:?}: {}[... snip ...]", pid, &p[..maxoff]);
} else {
debug!("{:?}: {}", pid, p);
}
}
}
let (mut asts, mut hirs) = (vec![], vec![]);
for (pid, p) in patterns.iter().with_pattern_ids() {
let ast = self
.ast
.build()
.parse(p.as_ref())
.map_err(|err| BuildError::ast(pid, err))?;
asts.push(ast);
}
for ((pid, p), ast) in
patterns.iter().with_pattern_ids().zip(asts.iter())
{
let hir = self
.hir
.build()
.translate(p.as_ref(), ast)
.map_err(|err| BuildError::hir(pid, err))?;
hirs.push(hir);
}
self.build_many_from_hir(&hirs)
}
/// Builds a `Regex` directly from an `Hir` expression.
///
/// This is useful if you needed to parse a pattern string into an `Hir`
/// for other reasons (such as analysis or transformations). This routine
/// permits building a `Regex` directly from the `Hir` expression instead
/// of first converting the `Hir` back to a pattern string.
///
/// When using this method, any options set via [`Builder::syntax`] are
/// ignored. Namely, the syntax options only apply when parsing a pattern
/// string, which isn't relevant here.
///
/// If there was a problem building the underlying regex matcher for the
/// given `Hir`, then an error is returned.
///
/// # Example
///
/// This example shows how one can hand-construct an `Hir` expression and
/// build a regex from it without doing any parsing at all.
///
/// ```
/// use {
/// regex_automata::{meta::Regex, Match},
/// regex_syntax::hir::{Hir, Look},
/// };
///
/// // (?Rm)^foo$
/// let hir = Hir::concat(vec![
/// Hir::look(Look::StartCRLF),
/// Hir::literal("foo".as_bytes()),
/// Hir::look(Look::EndCRLF),
/// ]);
/// let re = Regex::builder()
/// .build_from_hir(&hir)?;
/// let hay = "\r\nfoo\r\n";
/// assert_eq!(Some(Match::must(0, 2..5)), re.find(hay));
///
/// Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn build_from_hir(&self, hir: &Hir) -> Result<Regex, BuildError> {
self.build_many_from_hir(&[hir])
}
/// Builds a `Regex` directly from many `Hir` expressions.
///
/// This is useful if you needed to parse pattern strings into `Hir`
/// expressions for other reasons (such as analysis or transformations).
/// This routine permits building a `Regex` directly from the `Hir`
/// expressions instead of first converting the `Hir` expressions back to
/// pattern strings.
///
/// When using this method, any options set via [`Builder::syntax`] are
/// ignored. Namely, the syntax options only apply when parsing a pattern
/// string, which isn't relevant here.
///
/// If there was a problem building the underlying regex matcher for the
/// given `Hir` expressions, then an error is returned.
///
/// Note that unlike [`Builder::build_many`], this can only fail as a
/// result of building the underlying matcher. In that case, there is
/// no single `Hir` expression that can be isolated as a reason for the
/// failure. So if this routine fails, it's not possible to determine which
/// `Hir` expression caused the failure.
///
/// # Example
///
/// This example shows how one can hand-construct multiple `Hir`
/// expressions and build a single regex from them without doing any
/// parsing at all.
///
/// ```
/// use {
/// regex_automata::{meta::Regex, Match},
/// regex_syntax::hir::{Hir, Look},
/// };
///
/// // (?Rm)^foo$
/// let hir1 = Hir::concat(vec![
/// Hir::look(Look::StartCRLF),
/// Hir::literal("foo".as_bytes()),
/// Hir::look(Look::EndCRLF),
/// ]);
/// // (?Rm)^bar$
/// let hir2 = Hir::concat(vec![
/// Hir::look(Look::StartCRLF),
/// Hir::literal("bar".as_bytes()),
/// Hir::look(Look::EndCRLF),
/// ]);
/// let re = Regex::builder()
/// .build_many_from_hir(&[&hir1, &hir2])?;
/// let hay = "\r\nfoo\r\nbar";
/// let got: Vec<Match> = re.find_iter(hay).collect();
/// let expected = vec![
/// Match::must(0, 2..5),
/// Match::must(1, 7..10),
/// ];
/// assert_eq!(expected, got);
///
/// Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn build_many_from_hir<H: Borrow<Hir>>(
&self,
hirs: &[H],
) -> Result<Regex, BuildError> {
let config = self.config.clone();
// We collect the HIRs into a vec so we can write internal routines
// with '&[&Hir]'. i.e., Don't use generics everywhere to keep code
// bloat down..
let hirs: Vec<&Hir> = hirs.iter().map(|hir| hir.borrow()).collect();
let info = RegexInfo::new(config, &hirs);
let strat = strategy::new(&info, &hirs)?;
let pool = {
let strat = Arc::clone(&strat);
let create: CachePoolFn = Box::new(move || strat.create_cache());
Pool::new(create)
};
Ok(Regex { imp: Arc::new(RegexI { strat, info }), pool })
}
/// Configure the behavior of a `Regex`.
///
/// This configuration controls non-syntax options related to the behavior
/// of a `Regex`. This includes things like whether empty matches can split
/// a codepoint, prefilters, line terminators and a long list of options
/// for configuring which regex engines the meta regex engine will be able
/// to use internally.
///
/// # Example
///
/// This example shows how to disable UTF-8 empty mode. This will permit
/// empty matches to occur between the UTF-8 encoding of a codepoint.
///
/// ```
/// use regex_automata::{meta::Regex, Match};
///
/// let re = Regex::new("")?;
/// let got: Vec<Match> = re.find_iter("☃").collect();
/// // Matches only occur at the beginning and end of the snowman.
/// assert_eq!(got, vec![
/// Match::must(0, 0..0),
/// Match::must(0, 3..3),
/// ]);
///
/// let re = Regex::builder()
/// .configure(Regex::config().utf8_empty(false))
/// .build("")?;
/// let got: Vec<Match> = re.find_iter("☃").collect();
/// // Matches now occur at every position!
/// assert_eq!(got, vec![
/// Match::must(0, 0..0),
/// Match::must(0, 1..1),
/// Match::must(0, 2..2),
/// Match::must(0, 3..3),
/// ]);
///
/// Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn configure(&mut self, config: Config) -> &mut Builder {
self.config = self.config.overwrite(config);
self
}
/// Configure the syntax options when parsing a pattern string while
/// building a `Regex`.
///
/// These options _only_ apply when [`Builder::build`] or [`Builder::build_many`]
/// are used. The other build methods accept `Hir` values, which have
/// already been parsed.
///
/// # Example
///
/// This example shows how to enable case insensitive mode.
///
/// ```
/// use regex_automata::{meta::Regex, util::syntax, Match};
///
/// let re = Regex::builder()
/// .syntax(syntax::Config::new().case_insensitive(true))
/// .build(r"δ")?;
/// assert_eq!(Some(Match::must(0, 0..2)), re.find(r"Δ"));
///
/// Ok::<(), Box<dyn std::error::Error>>(())
/// ```
pub fn syntax(
&mut self,
config: crate::util::syntax::Config,
) -> &mut Builder {
config.apply_ast(&mut self.ast);
config.apply_hir(&mut self.hir);
self
}
}
#[cfg(test)]
mod tests {
use super::*;
// I found this in the course of building out the benchmark suite for
// rebar.
#[test]
fn regression_suffix_literal_count() {
let _ = env_logger::try_init();
let re = Regex::new(r"[a-zA-Z]+ing").unwrap();
assert_eq!(1, re.find_iter("tingling").count());
}
}
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